Welcome to a very special session. This lesson takes us into a deeply personal conversation about the nature of our own “moment-by-moment” reality.

To understand the biology of subjectivity, we must move beyond looking at the brain as a collection of parts and start looking at the “story” it tells. We have spent our previous lessons building the brain from the ground up, mapping the “street map“ of fiber tracts and the “traffic flow“ of 100 trillion connections. Now, we must ask: what is all that activity actually for?

We have a growing understanding of many relationships between the structure and functions of the brain and our own private experiences. If there is a chasm between subjectivity and the brain, it has not been discovered so far.

We often talk about the brain’s “hardware,” but today we are talking about the “software” of the self—subjectivity. In Mini-Course #8, we examine our living, private narrative and ask: what does subjectivity actually mean?

We have brought together a brilliant group of thinkers to help us define what it means to be “me.”

Dr. Jay Giedd: The “Story” of Connectivity

Jay looks at the brain from a developmental perspective. He asks a profound question: if not in the womb, at what point in life and in our brain’s development do we first have the sensation of being “me”?

To Jay, subjectivity is not found in a single brain structure, but in interconnectedness.

He uses a beautiful analogy: think of brain parts as letters of the alphabet. Alone, they are just A, B, and C. But as the brain matures, those letters connect into words, then sentences, and eventually a story. Consciousness—and subjectivity—emerges when the brain crosses a threshold of connectivity where those “sentences” become a narrative of the world around us and the world within us.

On the emergence of the conscious narrative:

"I think that the key to consciousness, so to speak, will be in understanding of how these connections and if the different brain parts are like letters of the alphabet... they have become a story. And that is when consciousness emerges."

David Edelman: The Privileged “You-ness”

David reminds us of the privileged nature of your experience. You are absolutely unique. I can never truly experience the world exactly as you do because you have a unique history that I do not share. We call this the “Jay-ness of Jay” or the “David-ness of David”.

Subjectivity is interactive. It’s not just the connections we are born with; it’s the selection by the world and our own history that strengthens certain neural pathways while others weaken or die off. Your subjective self is a physical record of your unique path through the world.

On the private nature of the individual:

“You are you, and I have no direct access to the units of you. This is you, you are absolutely unique. And there is no way that I could possibly experience the world the way you experience the world, however well, or however much you try to communicate that to me.”

Jeffrey Krichmar: Mental Time Travel and Empathy

For Jeff, a big part of the subjective experience is memory. We use our memories to engage in “mental time travel”—looking back to shape who we are and looking forward to plan the future. Over a lifetime, we develop values that act as filters for how we process those memories.

He also highlights Theory of Mind and empathy. Because we are social creatures, our subjectivity allows us to put ourselves in someone else’s shoes. This is highly adaptive; it helps us anticipate alliances and understand what others are doing, which is vital for survival in a group.

On the role of memory and forward planning:

"I think memories are a big part of subjective experience—how you can use those memories to kind of do mental time travel, to work through those memories, to actually plan for the future."

Mark Mitton: The Magic of Complexity

Finally, our friend Mark Mitton gives us the magician’s perspective. He points out that psychologists often get trapped in a “verbal world” of asking questions, while a magician knows that subjectivity starts much earlier—think of how a child “works” their parents long before they can talk about it.

Mark argues that the line between subjective and objective blurs when we align or “couple” with other people through eye contact and interaction. He also offers a crucial critique: scientists often focus too much on attention control, forgetting that confusion is a major part of how humans fool each other and navigate the world. Subjectivity isn’t a simple “A causes B” equation; it is a world of complexity.

On the necessity of embracing social and physical reality:

"When you go into the physical world and the social world, if you are not talking about complexity, you are not in the world."

🧩 The Subjectivity Quiz

This short quiz will help you develop some of the key ideas from Mini-Course #8. No pressure — just have fun! 🔠

Question 1

According to Jay Giedd’s alphabet analogy, when does consciousness or subjectivity emerge?

• A) When the brain reaches its maximum physical size.

• C) When a baby is first born.

• B) When individual brain parts (letters) become sufficiently interconnected to form a “story.”

✅ Answer: C Giedd emphasizes that the "key to consciousness" is interconnectedness. Just as a story is more than just a pile of letters, your subjectivity is the result of your brain parts crossing a threshold of connectivity that allows for memory and references to the internal and external world.

Question 2

What does David Edelman mean by the “privileged nature” of subjective experience?

• A) That only scientists are allowed to study it.

• B) That your history and perception are unique to you, and no one else has direct access to them.

• C) That some people have more consciousness than others.

✅ Answer: B Edelman points out that your "you-ness" is private and privileged. Because your physical eyes see differently and your history is unique to you, even another human cannot have an identical experience

Question 3

Jeffrey Krichmar suggests we use memories for “mental time travel.” What is the purpose of this?

• A) To forget painful experiences.

• B) To work through the past and plan for the future.

• C) To replace subjective thoughts with objective data.

✅ Answer: B Subjectivity is dynamic. Krichmar points out that we build memories and then use those memories—filtered through our values—to navigate time. This allows us to plan and evolve based on our personal history.

Question 4

Why does magician Mark Mitton argue that confusion is an important part of the human experience?

• A) Because humans use confusion to “work” and fool each other in complex social interactions.

• B) Because it makes simple predictive models of attention easier to understand.

• C) Because it is the opposite of subjectivity.

✅ Answer: A Mitton suggests that the social world is far more complex than simple "A causes B" logic. By understanding how we use confusion and "aligning" with others, we see that subjectivity is about the messy, selective reality of human connection.

⏰ YOUR 2 MINUTES ON SUBJECTIVITY

Now, I would like to invite you into the very same selective environment our panel navigated. Nat Geld posed a challenge to our experts that I now pose to you: take exactly two minutes to reflect on your own “individual, moment-by-moment” reality.

What do you mean when you say subjectivity or a subjective experience? How would you demonstrate the privileged nature of your own “you-ness”?

As you prepare to write, I want you to consider the different “letters” of your life—the neural architecture and connectivity that have finally connected into words, sentences, and your own personal “story”.

Think about the fact that your history is yours alone; even though we are all human, your eyes see the world somewhat differently, and no one else can ever have an identical experience.

You might explore your own mental time travel, using your built-up memories and personal values to work through the past and plan for the future.

Or, perhaps you find subjectivity in the way you align and couple” with others through a shared joke or a moment of empathy.

Or something else entirely…

No worries about the verbal world of formal definitions or simplistic “A causes B” logic. Instead, embrace the complexity and the sloppiness of being a social creature. It’s all so interesting.

— WHAT IS SUBJECTIVITY? —

Ready? Your two minutes start now.

Image Credits:

Visualization of MRI brain scan data from a single person, showing nerve fiber bundles near or feeding into part of the hippocampus. Neuroscientist Tyler Ard, NIH-supported lab of Arthur Toga, Keck School of Medicine, University of Southern California, Los Angeles

Jim Stanis, Arthur W. Toga, Ryan Cabeen, Laboratory of Neuro Imaging (LONI), USC Stevens Neuroimaging and Informatics Institute; NIH Brain initiative 2019

Network architecture of the long-distance pathways in the macaque brain. Dharmendra S. Modha, Raghavendra Singh. Proceedings of the National Academy of Sciences Jul 2010, 107 (30) 13485-13490; DOI: 10.1073/pnas.1008054107

🧵 In case you missed it, here’s Mini-Course #1: Your Stream of Consciousness 🕊️

🧵 Mini-Courses Archive

There are many ways in which the nervous system adapts to some conscious event, thereby reducing conscious access to it. But the opposite process occurs as well: There is extensive evidence that people seek out novel and informative conscious contents. We do not wait for the perceptual world to fade. We always go on to seek new and interesting things.

In sum, there seem to be two tendencies: one to reduce conscious access by adaptation, and a countervailing tendency to increase conscious access by searching for informative stimulation. These two tendencies may alternate, so that we seek conscious information, adapt to it, seek a new source of information, adapt to that, and so on. The process may approach a self-regulating homeostasis that tends toward optimal information flow.

Here we explore the search for information at different levels of conscious access: in perception, in conceptual processes, and in the domain of goals, where the search for information helps to define the significance of conscious input.

Perceptual systems aim for informative parts of the field

In nature, all of an animal’s senses work together in active, coherent exploration. Upon hearing a surprising noise, a dog will prick up its ears; it will look toward the sound; its pupils will dilate, lungs expand to help sniff the air, nostrils flare to allow better smelling; the animal will even taste the in-breathed air as it flows over the tongue.

If the sound is interesting the dog will move toward it, constantly sniffing — looking, listening, and licking anything of interest. It is actively searching for information, for signals that make a difference in the search for food, for social and sexual partners, for dangers to avoid, and often for just plain novelty.

In the laboratory, by contrast, we usually examine only one perceptual system at a time; but the same overwhelming preference for information emerges there. There is extensive evidence that eye-movements focus on the most informative parts of a scene. Given a choice between predictable and unpredictable figures, people choose those that are moderately unpredictable: those with enough information to be interesting, but not so much as to be confusing or overwhelming with novelty. And it is well established that animals and people will work for informative stimulation without food or any other reward.

The same restless search for information characterizes conceptual processes, those that are abstract and not directly reducible to perception or imagery.'

Conceptual processes aim for informative points

“Be informative” is a cardinal rule of normal discourse. In fact, violations of this rule are quite strange. When the same conceptual message is repeated over and over, we tend to turn away to other, more interesting and informative material. If we nevertheless try to pay attention to the same redundant material, we find that doing this is quite effortful, and ultimately impossible.

People do not ask questions about the things they already know — we always speak with a point of information in mind, either for the speaker or the listener. All these facts suggest that people seek conceptual information in the sense described above.

But what about apparent exceptions, such as repeated insistent demands for help, or a child’s pursuit of some desire? Surely messages like this can be repeated hundreds of times without adding new information. What about obsessive thoughts, which may recur thousands of times?

All of these cases can be reconciled with the idea that people search for novel information, if we interpret them within a goal frame. Goal frames are much more lasting and invariant than perceptual frames, and the same perceptual message — “Can I have that toy?” — may be repeated over and over again without losing its informativeness in the goal frame.

These phenomena can be described in the same terms, with the difference that conceptual processes involve a more abstract level of representation. Clearly the search for information can operate at many levels of representation, just as adaptation to information occurs at all levels of representation.

Read more

Welcome to a truly wonderful moment in our study of the brain. We are moving beyond static pictures to look at the living, active “wiring” of a human being. We’ve entered a groundbreaking era of neuroscience, where MRI technology allows us to see truly fine detail through a person’s whole brain. No longer limited to the surface; we can now visualize the actual nerve fiber tracts feeding into deep structures like the hippocampus, which is the vital region for creating new memories.

In Mini-Course #7, we relate our previous look at the circular representation of the “Cerebral Connectome” with a high resolution view of actual living fiber tracts — which make “any-to-any” signaling possible in our brain’s enormous network of 100 billion neurons and its 100 trillion connections.

We are looking at a truly beautiful sight: the white fiber tracts that pervade the brain and spinal cord.

These are the great highways of the nervous system, connecting distant points to coordinate an enormously complicated system. By tracing these living fiber tracts, we are able to build the “Connectome”—the definitive “street map” of the cerebral cortex that reveals how sensory input and motor output flow in and out of our conscious workspace.

Hippocampal Connectivity

This visualization of MRI brain scan data is from a single person, showing nerve fiber bundles near or feeding into part of the hippocampus.1

Symmetry and the Bridge

As we rotate our visualization, the vertical symmetry of the brain is striking. You can see the left and right hemispheres working as mirror images, held together by the corpus callosum—the massive bridge that allows the two sides to coordinate.

If you look closely at these images, you see something quite wonderful. You see the fiber tracts growing upward from the spinal cord, moving through the brain stem, and then reaching way out to terminate in the cortex itself.

This is one set of highways flowing in and out of the cerebral cortex.

Notice the symmetry between the left and the right, and the corpus callosum bridging between the left and the right.

As we discussed in Mini-Course #6, we must distinguish between the structural connectome (the physical street map) and the functional connectome (the dynamic traffic flow). The fiber tracts we see in these MRI visualizations are the "streets." The actual "traffic" is the signal flow that shifts about 10 times per second, serving as the index of our momentary conscious experience.

The Power of "Any-to-Any" Signaling

What makes the cortico-thalamic system unique is its support for any-to-any signaling—allowing information to be globally broadcast from any region of the brain. In the 3-millimeter-thick outer layer of the cerebral cortex, which early anatomists naturally called “grey matter,” each small patch has many specialized cell bodies linked by long nerve fibers to all the other small patches in cortex, either directly or by way of the thalamus, the great way-station of the cortex.

• Horizontal and Vertical Flow: The cortex communicates horizontally from cell to cell and vertically between the cortex and the thalamus.

• Symmetry: This MRI visualization shows the left and right hemispheres, showing how distant patches of neurons can be wired together regardless of their physical proximity.

The structure and function of the living brain are intricately linked, through multiple levels and modes of brain connectivity. Remember that this street map is not fixed. Through learning, adaptation, and reorganization, or plasticity, the brain’s "road crews" expand the highways that get the most traffic. As we've learned, "neurons that fire together, wire together, and grow together".

A new connection isn't just a line on a map; it’s a living metabolic support system that grows stronger the more it is used. As you advance your knowledge and understanding with each new Mini-Course, your beautiful brain’s “great highways” strengthen and expand!

🧩 Short Quiz: Great Highways of the Living Brain

Q 1. What is one of the major breakthroughs of modern MRI technology?

• A) It can only see the surface of the brain.

• B) It allows us to see fine detail through the whole brain of a living person.

• C) It can only be used on non-living tissue.

✅ Answer B: We are in a groundbreaking era because we can now see "truly fine detail" throughout the whole brain of a living individual. This allows us to map out entire brain-wide circuits rather than just looking at isolated regions.

Q 2. Which brain region is specifically identified as allowing you to create new memories?

• A) The Spinal Cord

• B) The Corpus Callosum

• C) The Hippocampus

✅ Answer C: The hippocampus is a vital "neighborhood" in our mental city because it is the region that allows for the creation of new memories. We can now visualize the fiber bundles that "feed into" this area, helping us understand how memories are wired into the system.

Q 3. How are the fiber tracts described in relation to the spinal cord and cortex?

• A) They grow upward from the spinal cord and terminate in the cortex.

• B) They stay entirely within the brain stem.

• C) They grow downward from the hair follicles.

✅ Answer A: The brain is an enormous outgrowth of the spinal cord. These fiber tracts are the physical evidence of that growth, from the spinal cord into the brainstem, reaching all the way up through the cortex, acting as great highways for both sensory input and motor output.

Q 4. What is the “Connectome”?

• A) A type of MRI machine.

• B) The bridge between the left and right hemispheres.

• C) The map of connections, or “street map,” of the cerebral cortex.

✅ Answer C: The Connectome is the "street map of the brain". By tracing living fiber tracts, we are creating a functional and structural map that helps us understand how this enormously complicated system coordinates.

Explore more… LONI — Laboratory of Neuro Imaging

Researchers at LONI are using advanced imaging technologies and techniques to create the world’s most detailed map of connections inside the brain. Their goal is to increase the pace of discovery in neuroscience by better understanding how the brain works when it’s healthy and what goes wrong in disease.

🧵 KEEP LEARNING! Mini-Course Archives

The development of conceptual presuppositions gives us another example of frame creation through adaptation. We have previously suggested that all consciously accessible concepts exist within a framework of prior unconscious presuppositions. Without such presuppositions, the concepts themselves are different.

We may now suggest that this presupposed knowledge is often the result of previously conscious concepts.

When we first encounter someone from a different culture, we become conscious of many things that are normally presupposed. The person may speak from an uncomfortably close distance, or may reveal different conceptual assumptions in ordinary conversation. If we live for some time in that culture, such prominent features tend to disappear. They become part of the presupposed frame.

Then, when we encounter our old culture again, we may be surprised by features that had previously gone unnoticed. Previously presupposed ideas and actions now become conscious.

As usual, it is contrasts and transitions that bring out these points. Experts have much less conscious access to such material than novices.

We can refer to these phenomena as framing and deframing. When we encounter new assumptions about reality, we often need to make them explicit. That does not mean that we must define them verbally. It may be enough to contrast two different points of view — a politically rightist versus leftist viewpoint, for example.

Once we become familiar with the contrasts, they can become automatic and framed, or contextualized. They then shape subsequent thought without becoming conscious. If the new frame is violated, however, it may become deframed, or decontextualized. A contrast that was previously unconscious becomes conscious again.

Consider the process of constructing scientific reality, as in the discovery of the atom.

In modern times, the first serious proposals for the existence of atoms go back to Dalton in the early nineteenth century. Dalton proposed that tiny indivisible — Greek: atomic — particles of hydrogen and oxygen must combine in a two-to-one ratio to form water.

But this hypothesis did not establish the reality of atoms and molecules. It began a debate that continued for the rest of the nineteenth century, with many facts pro and con offered by both sides.

Some scientists refused to believe in atoms, or treated them only as useful fictions, façons de parler, without any reality. They had arguments in their favor. Not all substances fell apart into elements with simple ratios. The relationships between the supposed elements were confusing, and could not be organized coherently until quite late in the century.

The reality of atoms was not widely recognized until the various alternatives were shown to reduce to essentially one interpretation. This reduction in alternatives culminated with Einstein’s work early in the twentieth century. At that point, atoms became part of the conceptual framework of a new world view.

No longer were they considered merely convenient fictions. They were “real” objects.

In general, it appears that scientific constructs are not considered “real” until other ways of interpreting the evidence are lost from sight. At that point the community stops arguing about them, and begins to take the new construct for granted.

Newly “real” objects can then become the fulcrum of new explorations, which now presuppose the existence of the construct. Thus atoms have become part of the unquestioned frames within which modern physicists explore subnuclear particles.

For scientific constructs like atoms, it is not so much that they disappear from the consciousness of the scientists who accept them. Rather, the construct is accepted when alternatives are forgotten.

Thus in particle physics today, no one ordinarily challenges the reality of atoms. To do that would undermine the task of exploring subatomic and subnuclear particles. It would force researchers to challenge the frames within which protons and quarks are defined.

Challenging frames is possible, of course.

Einstein’s relativity theory decontextualized, or deframed, Newtonian presuppositions about space and time. Quantum mechanics decontextualized Einstein’s assumptions about determinism. In both cases, physicists became conscious once more of the alternatives to their presupposed reality.

But it is difficult to decontextualize one’s assumptions and at the same time engage topics within those assumptions. In driving a car, one cannot be absorbed in moving the steering wheel and successfully engage the road at the same time.

In general, a frame must remain stable, presupposed, and largely unconscious in order for us to engage the objects defined within it.

These parallels between a perceptual-motor task like driving a car and the pursuit of scientific reality are intriguing. They suggest that consciousness of the perceptual world and consciousness of a conceptual reality like science may follow similar laws.

Notions such as predictability and uncertainty, informativeness and redundancy, framing, context of alternatives, and deframing may have very wide application.

The thrust of this argument is that human beings adapt to information at all levels: perceptually, imaginatively, conceptually, motorically, and even motivationally. As they adapt, they lose conscious access to the learned material.

But people also seek informative input. Thus there are two countervailing tendencies: we adapt to information until it becomes part of the unconscious frame, and we seek new information that can bring the frame itself back into consciousness.

The cerebral cortex fills the top half of our heads, and is actually a folded surface made up of hundreds of millions of cell bodies which can be mathematically unfolded into one single sheet a few millimeters thick, and is about the size of a dinner napkin.

The flat sheet of cortex is a six-cell layer mosaic of many specialized patches of tissue. In some patches each cell signals a face or a building; in others they show a harmonic series of auditory frequencies; in yet other regions, maps of the body are represented by neurons and small patches of cells. Neurons are signaling cells with long, thin branches.

Harvard connectomics researcher Allen Lee says that “many of us have seen microscopic images of neurons in the brain — each neuron appearing as a glowing cell in a vast sea of blackness. This image is misleading: Neurons don’t exist in isolation. Each cell in the layers of the cortex spreads out thousands of branches to other cells, and so to understand what a single neuron is doing, ideally you study it within the context of the rest of the neural network.”

About 25 billion cell bodies reside in the cortical sheet itself, and all their branches — dendrites and axons — either flow toward the thalamus from cortex, or spread horizontally in a flat “feltwork,” a cloth made of billions of dendrites tangled in each others’ hair. The cortex therefore communicates both horizontally, from cell to cell, and vertically, from the cortex to the thalamus.1

This is the “cerebral connectome” — a massive network of about 100 billion neurons with more than 100 trillion different connections to each other — that makes the cortex and thalamus unique in the body.

The cerebral connectome reveals the major street map of the cortex.

What the “connectome” does for the first time in history, we believe, is create a genuine street map for the kinds of connectivities in nature. The traffic map of the cortex is called the “functional connectome” because it is not a static map, but a dynamic map that shows the epicenter of the traffic flow at any given moment in time.

When you are conscious of sound, more of the traffic is coming from your auditory cortex. When you emphasize vision (as in the case of reading), more of the brain traffic is likely to come from the large visual cortex that lives at the very rear of the brain.

The signal traffic that flows over the great street map called the “connectome” may be even more important, much as auto traffic flowing over a street grid in a city is more important than the size of the streets. Rush hour traffic early in the day gives us a way of thinking about peak traffic flow; flow is related to the traffic capacity of streets, but it is a separate variable, and it may give us a better index of the actual work of processing in the brain in any given moment. In such a signal flow, the momentary peak flow may indicate our momentary conscious experience (believed to change about 10 times per second).

The brain’s version of a global workspace must unify that street map from one experience to the next. It is a very important new insight.

This distinction between structural and functional is fundamental, but it’s not absolute. If we think of structure as a street map of cortex, and function as the flow of traffic along those streets, then there is a dynamic relationship between the two. If the streets are heavily traveled, traffic engineers will have to make them wider and stronger.

We can imagine a wave of traffic being followed by a street crew that automatically expands the road so that the functional flow of traffic affects changes in structure of the road. This is called plasticity—learning, adaption, and reorganization.

The Hebbian rule of learning is that “neurons that fire together, wire together.” This is a useful rule of thumb, and it drives many neural net models of particular brain functions. But it is not quite right. Dr. Jay Giedd suggests that the Hebbian rule be expanded to “neurons that fire together, wire together, and grow together.” A new synapse, a new connection requires an entire metabolic support apparatus which allows the whole system of connective tissue to expand, grow stronger, and require more metabolic fuel. The relationship between structural units is therefore very dynamic.

The Wiring: Neurons & their links in the cortico-thalamic system.

We can think of the connectome as a “wiring diagram.” Figure 2 below shows the enormous network of neural connections that keep the cortex working. Many scientists have studied specific cortical pathways over the years, but this figure is one of the first published efforts to put them all together, thanks to Irimia, Chambers, Torgerson, and VanHorn, introducing an innovative framework for the depiction of human connectomics by employing a circular visualization method which is highly suitable to the exploration of central nervous system architecture.2

The C-T complex supports any-to-any signaling.

In the 3-millimeter-thick outer layer of grey cells of the cerebral cortex, which early anatomists naturally called “grey matter,” each small patch has many specialized cell bodies linked by long nerve fibers to all the other small patches in cortex, either directly or by way of the thalamus, the great way-station of the cortex.

• Those specialized neurons are shown in the outer rim of the connectogram of Figure 2 and 3, each patch with its own color.

• In the middle of the connectogram, the authors have shown the long axons that connect the thin rind of cortical cell bodies to each other.

• This diagram does not show all the “cortico-cortical” connections, because that would make it impossible to see individual lines. But this connectivity diagram gives us one of the clearest visuals we have today.

The cortico-thalamic system allows any spatiotopic activity (SA) array to signal any other. Combined with adaptive resonance, this allows an open set of cortical and thalamic coalitions to bind and broadcast information from any region to any other. The left half represents the left hemisphere of the brain, whereas the right half represents the right hemisphere. The brain stem is shown at the bottom. Circular color bars at the bottom describe the scale of the corresponding anatomical ring.

The significance of the connectome stems from the realization that the structure and function of any brain are intricately linked, through multiple levels and modes of brain connectivity. There are strong natural constraints on which neurons or neural populations can interact, or how strong or direct their interactions are. Indeed, the foundation of human cognition lies in the pattern of dynamic interactions shaped by the connectome.

Despite such complex and variable structure-function mappings, connectomes are an indispensable basis for the mechanistic interpretation of dynamic brain data, from single-cell recordings to functional neuroimaging.

A view of the tangle of cortical “feltwork”

For perspective, this video of the “functional connectomics spanning multiple areas of the mouse visual cortex” was made by Tyler Sloan, PhD, and is beginning to reveal how structure is related to function.

From just one cubic millimetre of mouse brain — about the size of a chia seed — around 84,000 neurons, half a billion synapses, and approximately 5.4 kilometres of neuronal wiring are traced with newly developed artificial intelligence tools. Although only a small fraction of the brain is represented, the high-resolution connectivity maps help to describe how the brain is organized and how the different types of cell work together.

The MICrONS Consortium (Machine Intelligence from Cortical Networks) of scientists present the largest, most detailed, functional wiring diagram of a mammalian brain to date — a milestone for neuroscience achieved by a global consortium of scientists. Understanding how the brain works—its parts, the way it is organized, how neurons are connected — scientists can better understand what happens when things go wrong in disease.

The Machine Intelligence from Cortical Networks (MICrONS) Project took seven years and is considered one of the most challenging neuroscience experiment ever attempted.3 An unprecedented dataset of high resolution anatomical images of individual cells in mouse visual cortex, mapped on to their responses. This integrated view of function and structure lays a foundation for discovering the computational bases of cortical circuits.4

Explore More… The MICrONS Project

🧩 Short Quiz: The Street Map & The Traffic Flow

Q 1 . If the structural connectome is the “street map” of the brain, what is the functional connectome?

• A) A static blueprint showing the size of every neuron.

• B) A dynamic “traffic map” showing the epicenter of activity at any given moment.

• C) The physical layer of glial cells that holds the neurons in place.

✅ Answer: B While the structural connectome reveals the major "highways and byways," the functional connectome is dynamic. Just as auto traffic in a city is more telling than the size of the streets, the flow of neural signals tells us what the brain is actually doing—whether you are focused on the "traffic" of the auditory cortex while listening to music or the visual cortex while reading

Q 2 . Which concept explains why a heavily used neural pathway might become physically stronger or “wider”?

• A) Any-to-any signaling.

• B) Momentary peak flow.

• C) Plasticity (Neurons that fire, wire, and grow together).

✅ Answer: C The relationship between structure and function is not absolute. Through plasticity, a wave of traffic is followed by a "street crew" that automatically expands the road. This is the expanded Hebbian rule: "neurons that fire together, wire together, and grow together," requiring a full metabolic support apparatus to strengthen the connection

Q 3. What is the significance of “any-to-any signaling” in the cortico-thalamic complex?

• A) It allows any region of the brain to broadcast information to any other region.

• B) It ensures that the left and right hemispheres never communicate.

• C) It limits signaling to only the “neighboring” patches of neurons.

✅ Answer: A The connectome is not just a "feltwork" of random tangles; it is a highly organized any-to-any signaling system. This allows specialized patches of the cortex—like those that recognize faces or buildings—to bind and broadcast information across the entire global workspace

Q 4. According to the “traffic” analogy, what serves as a potential index of our momentary conscious experience?

• A) The total number of synapses in a single cubic millimeter.

• B) The momentary peak flow of signal traffic, changing about 10 times per second.

• C) The color-coded rings on the outer edge of a connectogram.

✅ Answer: B Much like "rush hour" indicates peak activity in a city, the momentary peak flow in the brain’s traffic grid is believed to be the signature of conscious experience. This peak flow is incredibly fast, shifting roughly 10 times per second, reflecting the constant, flickering updates of our awareness

What happens after a conscious event has been successfully matched?

The first answer is that it does not simply disappear. It may no longer occupy consciousness, but that does not mean that it has ceased to function. Rather, it may have changed its role in the system.

The suggestion is this: conscious experience can help create the frames that shape later conscious experience. What is conscious at one moment may later become part of the background against which new events are noticed, interpreted, and understood.

This is a basic fact about adaptation. When the nervous system adapts to some input, that input may become predictable. Once it becomes predictable, it no longer needs to remain at the center of consciousness. But it has not vanished. It has become part of the frame.

William James noticed something important about this. When thunder crashes, what we hear is not thunder in isolation. We hear thunder breaking upon silence, and contrasting with silence. The prior silence matters. The nervous system had adapted to it. It had come to expect its continuation. The thunder therefore violates that expectation, and for that reason it becomes informative.

The silence, then, is not nothing. It is part of the frame that makes the thunder meaningful.

The same principle can be seen in ordinary skilled action.

Consider learning to drive a car.

When we first learn to drive, we may be very conscious of the steering wheel, the foot pedals, the gear lever, and the force needed to move each of them. We do not yet have the “feel” of the car. These actions present many open alternatives. How much pressure is needed on the accelerator? How far should the steering wheel be turned? How exactly should the gear lever be moved?

At that stage, the mechanics of driving are conscious.

But once we have learned to drive, those details usually recede. We no longer attend to every movement of the wheel or every small pressure of the foot. Instead, we become conscious of the road: its turns, traffic, pedestrians, other cars, signs, and destinations. The mechanics of driving have become part of the unconscious frame within which the road is experienced.

Notice that they have not disappeared. The nervous system continues to represent and regulate them. But their functional role has changed. They are no longer the main contents of consciousness. They are now among the conditions that make other contents possible.

Even the road itself can later become framed.

If the route is familiar and predictable enough, we may stop being very conscious of the road as such. We may begin thinking instead about where we are going, what we plan to do when we arrive, or some longer-term goal. The road has now become part of the background. It has become presupposed.

In this way, things that were once conscious may become automatic. That is not a mere loss. It is a transformation. What had been an object of conscious experience becomes part of the ground against which later experience is organized.

Learning can therefore be understood, in one important sense, as a reduction of alternatives. Before learning, many possible actions must be consciously considered. After learning, many of those alternatives have been reduced to a single expected pattern. When the relevant complexity has been reduced enough, we often say that the skill has been learned.

The loss of consciousness that accompanies habituation and automatization may therefore be a sign that learning is complete.

But then a further question arises.

If the act of driving becomes automatic, why do we become conscious of the road?

Presumably because the road is now more informative for our purposes than the mechanics of driving. Dodging another car, turning a blind corner, or braking for a pedestrian are less predictable than the ordinary handling of the steering wheel. These events make a difference. They matter within the current frame of action.

In that sense, conscious events are closely tied to information. An event becomes conscious, in part, because it selects among alternatives that matter to the organism.

Goals also provide frames.

When we are driving, we do not usually remind ourselves consciously that we want to survive, avoid harming pedestrians, obey the law, and reach our destination. Those goals are usually implicit. But they shape what becomes conscious. A pedestrian in the road is not merely a visual stimulus. It is significant because of the goal frame within which it appears.

Not running over the pedestrian serves several goals at once: avoiding harm to another person, avoiding trouble with the law, preserving one’s own safety, and continuing toward one’s destination. Purposeful actions are informative because they select among alternatives within such goal hierarchies.

The important point is that goals need not be conscious in order to shape consciousness. Like other frames, they often operate as background conditions. They constrain what becomes relevant, what becomes surprising, and what becomes conscious.

But a frame does not have to remain unconscious forever.

It can be deframed.

Suppose we are accustomed to driving a car with power steering. One day the power steering fails. Suddenly the steering wheel becomes difficult to turn, especially at slow speeds. What had been automatic now becomes conscious again. Our old predictions about the force needed to turn the wheel are violated. Our strategy must change.

Now the act of turning the steering wheel becomes an object of conscious experience. What had been a single, smooth, predictable action decomposes into several alternatives. We notice, for example, that it is easier to turn the wheel when the car is moving. That was not a consideration before. Now it has become relevant.

In Global Workspace terms, the newly conscious information can be globally displayed, so that it can influence the larger goal of steering the car.

The same principle applies quite generally.

When we break an arm, the arm is no longer merely part of the presupposed bodily background. It becomes an object of experience. Ordinary actions now involve conscious choices. The arm has become decontextualized. It has been pulled out of the background and made conscious again.

This gives us a useful way to think about frames.

Frames are not merely abstract structures imposed on experience from the outside. They consist, in part, of what the nervous system has already adapted to. They are the background against which new information is defined.

What is conscious today may become part of the unconscious frame tomorrow. And what has become unconscious background may return to consciousness when prediction fails, when action is disrupted, or when new alternatives become relevant.

Automaticity, then, should not be treated simply as a loss of consciousness.

It is also a gain in structure.

Conscious experience helps build the background that allows later conscious experience to occur.

In Mini-Course #5 on Consciousness & the Brain, we take a more anatomically realistic tour of the brain and nervous system: the thalamus as a downtown traffic hub, the hippocampus tucked into the temporal lobe like a sausage in a bun, the basal ganglia quietly coordinating every step you take, and the cortex divided at its central fold between the world coming in and your plans going out.

The Nervous System is Everywhere

We often think of the brain as sitting in a vacuum, but the spinal cord is actually a busy highway with “little branches” spreading neurons throughout your entire body. Your whole body has neurons, but they aren’t distributed evenly.

Think of your fingertips—they are incredibly dense with neurons compared to the back of your torso. Everything you feel or do flows through the spinal cord, either outgoing or in-going, flowing right into the lower brain stem.

The “Downtown” Traffic Hub of the Brain: Thalamus

In our last lesson, we saw the thalami as egg-shaped structures in the center. It’s tempting to call them the “center” of the brain, but that’s a bit misleading. In the “bird’s nest” of hemispheres sits the thalamus.

People tend to think it must be the center of the brain because of where it sits, but that’s not quite true. It’s more like the downtown of a city—it looks like the center, but the real story is the two-way traffic going back and forth between the thalamus and the cortex.

The thalamus is actually a part of the resonant cortico-thalamic system. Anatomy shows one thing, but physiology suggested a much larger, “unified oscillatory” functional system (Steriade, 1999).

"Sausage in a Bun": Hippocampus

If we look at the temporal lobe, which sticks out like an arm from the body of the brain, we find the hippocampus tucked inside. If you were to cut it just right, it looks like a sausage in a bun.

The "sausage" is the hippocampus, and right in front of it—though often covered up—is the amygdala, famous for fear processing and our basic survival.

The Engines of Action: Striatum and Putamen

Let’s look closer at those "shields" we called the basal ganglia. The word "basal" just means they are at the bottom, and "ganglia" means a clump of neurons. These are primarily concerned with output: controlling your body, your vocalization, and your forward planning. They consist of different nuclei: the striatum at the top (or dorsal) and the putamen in the middle.

Whether you are walking, vocalizing, or doing forward planning, your basal ganglia are constantly "talking" to each other to coordinate your every action.

The Cortical Landscape: Front vs. Rear

The cerebral cortex is a massive, adaptable organ. We can divide it at the central sulcus—a deep “valley” or fold in the middle.

• The Posterior (Rear): This is where conscious perception lives.

• The Frontal (Front): Especially enormous in humans, this is the seat of planning, speaking, and imagination.

While the two hemispheres look the same, the left frontal lobe is famously specialized for speech production and forethought.

The Crust & The Glue: Gray Matter and White Matter

When you slice the cortex like a loaf of bread, you see the white matter, which is composed of axons and myelin. It’s white because the neurons are surrounded by glial cells—the “glue” that early anatomists saw. But these aren’t just sticky fillers; they are support cells that feed, nurture, and resupply the neurons.

The gray matter is the very surface layer, a “crust” only six cell layers deep, composed of neuronal cell bodies, dendrites, and synapses. These neuronal cells are interlinked in a massive network of white matter connections, running in bundles, deeper in the brain.1

🧩 Short Quiz: Build-a-Brain II - Functional Matrix Tour

Question 1

Is the distribution of neurons the same throughout the entire human body?

• A) Yes, neurons are spread perfectly evenly.

• B) No, areas like the fingertips are much denser with neurons than the back of the torso.

• C) No, neurons are only found within the skull.

✅ Answer: B Neurons are not limited to the central nervous system; they innervate your whole body. However, density varies—your fingertips need many more neurons to manipulate and feel the world than the back of your torso does.

Question 2

Why is it misleading to call the thalamus the “center” of the brain?

• A) Because it is actually located in the cerebellum.

• B) Because its primary importance is the two-way traffic it exchanges with the cortex.

• C) Because it only exists in the right hemisphere.

✅ Answer: B While it resides in the middle of the "bird's nest," the thalamus functions as a traffic hub. The wiring goes in both directions, meaning it is defined by its constant communication with the cortex rather than being a static central point.

Question 3

In the “sausage in a bun” analogy of the temporal lobe, what structure represents the sausage?

• A) The Amygdala

• B) The Thalamus

• C) The Hippocampus

✅ Answer: C This vivid analogy shows how the temporal lobe (the "bun") houses the hippocampus (the "sausage"). The amygdala is the little "almond" that sits right in front of that sausage.

Question 4

What are the two major divisions of the basal ganglia mentioned?

• A) The Gray and White matter

• B) The Striatum and the Putamen

• C) The Frontal and Posterior lobes

✅ Answer: B The basal ganglia are more than just shields; they are complex "bottom clumps" of neurons. The top nuclei are the striatum and the middle nuclei are the putamen, both working together to control movement and forward planning

Question 5

What is the functional difference between the front and the back of the cerebral cortex?

• A) The back is for hearing, and the front is for seeing.

• B) The back is for conscious perception, while the front is for planning and speech.

• C) The back is for motor control, and the front is for sensory input.

✅ Answer: B The brain is organized by task. The posterior regions handle the intake of the world (perception), while the frontal regions—which are uniquely large in humans—handle the output: planning, forethought, and the production of speech.

From the “sausage in a bun” of our memory system to the six-layer-deep crust of our cortex, we see a system that is both incredibly complex and beautifully symmetrical. As you walk through the world today, remember that your basal ganglia are coordinating your steps while your posterior cortex is perceiving the beauty around you. 😊

Here is a central idea that has long seemed important to me.

Much of what guides conscious life is not conscious.

That may sound paradoxical, but it follows from a simple point: conscious experience is informative. When some aspect of experience becomes predictable, redundant, or fully expected, it tends to fade from consciousness, even though it may continue to shape thought and action.

This applies not only to perception, but to goals, meanings, and conceptual life as well.

When goals fade from consciousness

We can make a direct connection between goals, information, and consciousness, because redundant goals are lost from consciousness as well.

A graduate student may be very much aware, at the beginning of graduate education, of the goal of obtaining an advanced degree. But this goal tends to fade into the background as long as it remains highly predictable. Everyday concerns have more to do with the subgoals needed to carry out the goal of gaining an advanced degree than with this top-level goal. When the student goes to find a book in the library, it is not necessary to be reminded that this is done in pursuit of the ultimate goal.

A subgoal can even fail without bringing to mind the high-level goal. One may fail to find the right book in the library; one may even fail to pass an examination. However, if all subgoals fail without alternatives, the top goal also comes into question and must become conscious again. If money for school runs out, if the student has a disabling accident, and so forth, the top-level goal of gaining an advanced degree comes into consciousness, as alternatives to it need to be examined. But as long as goals are predictable, they are as unconscious as any other potentially conscious content.

In actual fact, the goal of gaining a graduate degree may be a poor example, because it is a socially agreed-upon goal, one that can be communicated to others for whom it is not redundant but informative. Thus the goal of gaining a graduate degree is fairly easy to access, even when it becomes routine, because it often needs to be communicated.

In the same way, teachers may be able to access information that practitioners will find more difficult to make conscious, because teachers must always be ready to communicate the presupposed information to students who do not share the presuppositions. From this point of view, it seems likely that constant private goals may be much more difficult to make conscious. Thus the goal of gaining the respect and affection of others may become presupposed and unconscious, even while we pursue its subgoals. Or the goal of advancing one’s social control, or of outshining competitors, may behave much like repression — that is to say, people will spontaneously disavow having such goals, even though the unconscious routine goals continue to guide their actions.

Redundancy effects are not limited to conscious processes

Conscious experience is not the only thing that habituates. Selective habituation to repeated input seems to be a universal property of neural tissue. Even a single neuron will respond to electrical stimulation at a given frequency only for a while; after that, it will cease responding to the original frequency, but continue to respond to other frequencies. For example, a pulse train of 300 Hz will cause the neuron to fire — until it habituates. After that point, it will no longer fire to a 300-Hz stimulus, though it will continue to respond to stimuli less than 280 Hz or more than 320 Hz.

Neuronal habituation is selective, just as habituation of the Orienting Response is selective. Further, Sokolov’s arguments also seem to apply at this level: fatigue cannot explain selective habituation, because the neuron continues to be responsive to nonhabituated frequencies. This kind of selective habituation can be observed at many different levels of organization in the nervous system: in single cells, in small assemblies of neurons, in larger nuclei and pathways, in complete sensory and motor systems, and in the nervous system as a whole.

This point is important theoretically, because it suggests that specialized processors attempt to adapt to input, and become quiescent when they have done so.

What, then, is the difference between local neural habituation and loss of conscious access to some experience? The proposal is that loss of conscious access is a global result of many cases of local habituation by specialized processors.

Conceptual redundancy effects

Habituation is not limited to perception. It may occur at all levels of analysis. Fading of conscious access to abstract concepts is shown by semantic satiation. A word repeated over and over again will soon seem different, somehow meaningless, estranged from its previous familiarity, as if it were being pronounced by some particularly impersonal robot. Semantic satiation is similar to stimulus habituation, but it seems to operate on the level of abstract meaning rather than sensation. It suggests, therefore, that the informativeness criterion does not apply only to perception and imagery, but to conceptual thought as well.

There has been some controversy about the empirical validity of semantic satiation, but the evidence for conceptual redundancy is actually quite pervasive. It is common for experts in any discipline, who do not need to communicate their expertise to novices, to find it difficult to retrieve their knowledge explicitly. This is likely to happen even though the inaccessible knowledge continues to inform their actions and experiences. Research on Adaptation Level Theory indicates that conceptual events are evaluated in a frame of alternatives that is shaped by previous experience with the same events.

Thus, one’s judged happiness is strongly affected by previous judgments of happiness. In general, when one achieves a new level of desired functioning — such as getting a higher level of income, a desired job, or a desired mate — people report high levels of happiness for some time. However, one rapidly becomes adapted to the new situation so that events are now evaluated with respect to the new Adaptation Level. The reported level of happiness then tends to decline relative to one’s expectations.

In addition, people frequently raise their sights again, so that they actually become unhappy relative to their new desired state. Naturally, the Adaptation Level at any particular time — the level of one’s successful predictions about the world — is not immediately consciously available, though it is established by conscious experiences and will become conscious again upon violation.

In general, those aspects of the world that we have learned most completely tend to be the least conscious.

That is the essential point. Consciousness is closely related to informativeness. What is unexpected, variable, or otherwise informative tends to become conscious. What is redundant tends to fade, even when it continues to shape thought and action.

This helps to explain why some of the most important determinants of conscious life may be the least conscious precisely because they have become so well learned.

Read more

Welcome to Mini-Course #4 in our Consciousness & The Brain Substack series.

To help you visualize the internal architecture of the human brain from the ground up, we use a "vertical build" approach, moving from the base of the central nervous system (CNS) to the outer layers of the cortex. We approach the architecture of the brain as if we are building it ourselves, step by step.

The human brain is not a random collection of parts; it is a highly organized, vertically symmetrical structure where the left and right sides are mirror images of each other. This lesson explores the brain as an enormous outgrowth of the spinal cord, built layer by layer to support life, movement, and complex thought.

Our narrated video lesson provides a fundamental understanding of your brain’s internal and external structures, their functions, and a little bit of lore behind their names.

🪞Vertical Symmetry

Just like your face and your body, the internal core of your brain is vertically symmetrical, meaning its internal structures are mirror images of one another. You have a left eye and a right eye, a left cheek and a right cheek, and on the inside, we see that same mirror-image organization.

This pattern is easily visible in our anatomy, but not necessarily in our biological functioning. Let’s look at this core of the brain, which essentially holds everything else in place.

The Foundation: The Brain Stem & The Bridge

Above the lower brain stem, we find the pons, a Latin term meaning “the bridge”

• Emerging from this “trunk” is the brain stem, much like the crown of a tree.

• Just above the lower brain stem sits the pons, a Latin term meaning “the bridge”.

This area serves as the essential core that holds the rest of the brain’s architecture in place.

The Inner Hub: Thalami and the Limbic System

Moving upward, sitting atop the core we find the thalami—two egg-shaped structures. We say “thalami” because they are plural.

• Each thalami “sprouts” outward to relate to its respective hemisphere: the left thalamus connects to the left hemisphere, and the right to the right.

Then, quite beautifully, we have the hippocampus. A nice way to remember this structure is to think of a rider on a horse with brown riding trousers.

• Hippocampus: These brown, curved structures resemble the legs of a “rider on a horse”.

At the very tip of the hippocampi sit the amygdalas. Early anatomists thought, “Gee, this looks like an almond,” so they used the Latin word for almond to name them.

• Amygdala: Located at the tips of the hippocampi, these are named after the Latin word for “almond” because of their distinct shape.

Elegant Spaces and Protective Shields: Ventricles and Basal Ganglia

One of the most elegant parts of the brain isn’t actually made of neurons. You can see the fluid ventricles in light blue, but they are not neural structures. Think of them as an internal circulatory system. You don’t want blood products getting into the brain, and you don’t want brain products in the bloodstream, so the ventricles feed important molecules to the tissue while keeping the systems separate.

• The fluid ventricles are spaces filled with cerebrospinal fluid. This acts as an internal circulatory system, delivering molecules and hormones to the CNS while keeping it protected from the primary bloodstream.

For physical interaction with the world, we have the basal ganglia, which look like a kind of shield on either side.

• Basal ganglia are for motor (muscular) control—and in anatomy, “motor” simply means “muscular”. If these are damaged, a person will have trouble with movement, walking, and likely speech.

The “Little Brain” and the Great Cortex

In the rear, straddling the brain stem, is the cerebellum, or “little brain”. It looks tremendously like the enormous cortex, just smaller, yet it is so densely packed that it has just about as many neurons as the cortex itself.

Finally, we reach the largest structure: the cerebrum, or simply, the cortex. When you look from the outside, you see the gray matter—the very surface layer.

Beneath it is the white matter, which is white because the neurons are surrounded by glial cells. Early anatomists, lacking high-powered microscopes, thought these cells looked like “glue”.

The cerebrum is the largest structure in the central nervous system. It is characterized by:

• Gray Matter: The very surface layer visible from the outside.

• White Matter: The layer beneath, which is white because neurons are surrounded by glial cells (which early anatomists thought looked like “glue”).

Altogether, this is a massive organization of some 100 billion cells.

The Conscious Aspect of Your Brain is also the Most Integrated Feature

A fundamental point about the brain is that, yes, speech output is located in Broca’s area in the left frontal cortex while speech input processing lives in the posterior region of both hemispheres. But speech output and input are highly integrated in healthy brains, because input and output are “functionally” integrated. The signals travel quickly enough so that in a healthy brain, input and output are essentially the same, integrated process.

This is also why your left eye is integrated with your right eye, why your left ear combines with your right ear in a single functional system, and why your right and left hands easily work together. These systems are functionally located to the left and right of your spinal cord, but they function in such close coordination that, in a healthy person, they are hard to separate.

These points apply to vertebrate nervous systems in general, but they may not apply to cephalopods, like the octopus, where the biggest brain is located in the head, while each arm has its own (smaller) brain. Those different locations are anatomical but not functional: a healthy octopus operates a highly integrated brain system when it is swimming forwards, for example.

The conscious aspect of your brain is also the most integrated feature: your two hands work well together because they are controlled by two symmetrical regions of the motor cortex on both sides. But when you walk, your hands tend to swing counter to your leg movements, which helps your whole body to balance more easily.

🧩 Short Quiz: “Build-a-Brain” Vertical Tour

Question 1

When we say the brain is “vertically symmetrical,” what does that mean for the internal structures like the thalami?

• A) There is only one thalamus located in the center.

• B) There are two, one on the left and one on the right, acting as mirror images.

• C) The structures are stacked on top of each other.

✅ Answer: B The core of the brain follows the same symmetry as your face. Just as you have a left and right eye, you have a left and right thalamus, each relating to its own hemisphere.

Question 2

Why did early anatomists name a part of the memory system the “amygdala”?

• A) It is the Latin word for “memory.”

• B) They thought it looked like an almond.

• C) It reminded them of a rider’s saddle.

✅ Answer: B Latin was once the universal language of medicine. Anatomists named things based on what they looked like; in this case, the small structure at the tip of the hippocampus looked exactly like an almond.

Question 3

The fluid ventricles are described as “elegant,” but what is their actual biological function?

• A) They process sensory information like sight and sound.

• B) They act as a shield to coordinate muscular movement.

• C) They serve as an internal circulatory system to feed the brain without using the bloodstream.

✅ Answer: C This is a crucial distinction—the ventricles are not neural. They are supply channels that deliver molecules and hormones, acting as a separate circulatory system because the brain needs to keep its “products” separate from the general bloodstream.

Question 4

Why is “white matter” white?

• A) It is made of pure bone for structural support.

• B) The neurons are surrounded by glial cells, which looked like “glue” to early scientists.

• C) It is the part of the brain that doesn’t contain any neurons.

✅ Answer: B The neurons themselves are grayish, but the white matter gets its color from glial cells. The name “glia” actually comes from the word for “glue,” because without modern microscopes, that is exactly what those cells appeared to be to early observers.

Take a moment to step back and see the whole picture of what we have built. I hope you carry this beautiful symmetry of your own internal architecture with you—not just as a collection of Latin names, but as a living "bridge" to understanding the deep logic of the human brain. 🧠✨

• In case you missed them, here’s the link to our previous Mini-Courses 🕊️

Conscious experiences can often be shown to involve not one, but at least two alternative representations, one of which is implicit. Whenever we become conscious of something, internal processes are saying, in effect, “Aha! It’s a dog with black and white spots, rather than a brown dog, or a cat, or some other object.” This kind of implicit comparison must take place at many levels of analysis at the same time.

Another way of saying this is that conscious events are objectlike: they have many correlated features, which are implicitly differentiated from potential alternatives. This is quite different from habituated representations, which are not experienced as objectlike.

A direct connection between conscious events and quantitative measures of information has been established in several cases. Objects fit into a hierarchy of abstraction, and the level that comes most readily to mind depends upon the alternatives that are being entertained. Depending on our purposes and implicit comparisons, different levels of the hierarchy are likely to come to mind.

There are other connections between likely conscious contents, implicit comparisons, and mathematical information theory. In communication, we select the most informative features to convey to the listener, that is, the features with the most valuable comparison. The framing of alternatives determines what is brought forward and what remains in the background.

This pattern is fundamental in linguistics. Conversations depend upon what is already shared, allowing new information to be brought to the fore. People seem to pay attention primarily to whatever is new, focal, topical, and emphasized. There is an implicit deemphasis of anything that is known, peripheral, and irrelevant at the moment.

If conscious events indeed exist in a frame of implicit alternatives, one sign of that fact may be their fleetingness.

It is very difficult to keep a conscious image in mind for more than a moment. One explanation is that adaptive processes are continually learning from conscious events, reducing their alternatives, and nibbling away at the information provided. If that is true, then most conscious events lose most of their information value very quickly, as uncertainty is reduced by adaptive mechanisms.

Finally, habituated or automatic events can become conscious again when their predictable conditions are violated. If they become unconscious due to redundancy, one way to make them conscious again is to violate the redundant pattern. Previously automatic features then become informative again, as they become conscious.

In that sense, consciousness is correlated with information content.

What becomes conscious does so not in isolation, but against a background of implicit alternatives.

In science, that’s perfectly normal. The greatest concepts — heat, gravity, life itself — were measured and used long before they were ever formally defined. Consciousness is no different.

In this Consciousness & The Brain Mini-Course #3, we explore how science builds its way toward understanding, not with perfect definitions handed down from above, but with careful observation, improving tools, plus a lot of ingenuity and patience. Bernard Baars and Nat Geld are joined by neuroscientist Dr. Alea Skwara, a Postdoctoral Scholar in Dr. Cliff Saron’s research group at the UC Davis Center for Mind and Brain, and Ilian Daskalov, a Cognitive Neuroscience Grad student from UC Irvine and IT Systems & Automation Specialist.

How do we build on the basic observations about consciousness?

Right now, as you read these words, thoughts and sounds are drifting in, feelings hover at the edge of your awareness or clench your chest or gut if you’re stressed, and your inner world hums in the background. That stream of consciousness is vivid, immediate, and deeply personal — and science has only recently begun to observe it directly.

Every living person has an individual stream of consciousness which has been celebrated by novelists and movie makers for many years, but scientists have only recently observed the brain state which goes along with the stream of consciousness (SoC).

This brain state occurs only during waking, and it is sometimes called the “Default State”, although it is extremely active: all you have to do is close your eyes for a minute and notice how many thoughts and feelings and subtle intuitions come to mind spontaneously without ever really being called to mind on purpose.

Your own spontaneous thoughts are highly relevant. They are your way of observing what humans and other animals have running through their minds and brains during all your waking hours, and even during their dreams. You don’t need a sensory deprivation chamber to observe your own stream of consciousness. But because the stream of consciousness is so complex, scientists have found it very difficult to study it in great detail until recently, when spontaneous brain activities that are not highly focused voluntary tasks but are more like free associations have been observed directly in the cortex.

In science, how do we begin to define a difficult concept like consciousness?

Many people ask for a definition of consciousness. Or they simply tell us that nobody knows what it is, so it must be impossible to understand. But this is a misunderstanding of the way empirical science works.

Science rarely begins with good definitions.

In the history of science, we never begin with theoretical definitions because we simply do not know what the ultimate definition will be: fundamental ideas like life, gravity, and heat. So we start with the simplest plausible guess, which is called an “operational definition”.

The Importance of Observational Definitions

One famous operational definition for heat was devised by the Italian Renaissance scientist, Galileo, who figured out the first thermometer — a very simple glass tube filled with water with little colored glass jars floating inside. That thermometer was probably good enough to show the temperature difference between noon and evening in Italy. It took another four centuries for the ultimate definition of heat to emerge in thermodynamics, which is our present theoretical definition of heat.

Rather, scientific concepts like “heat,” “force” and “momentum” evolve over long periods of time, inductively, not deductively. The thermodynamic definition of “heat” only emerged in the late 19th century. Humans certainly had ideas about “heat” long before Maxwell, and scientists from Galileo to Fahrenheit developed increasingly better ways to measure heat, but without basic 19th century discoveries about the physics of molecular motion and the Kelvin scale, it was useless to demand a theoretical definition of “heat.”

This very basic point about inductive science is still often misunderstood. Early empirical measures of new constructs are rarely adequate or complete.

Likewise, asking for a definition of “consciousness” is not useful at the beginning of a research program. Instead, we now have a large set of observable operations that tell us when a person is conscious. We keep improving our measuring tools whenever possible. (See Table 1.)

The traditional and most widely used index of conscious events is “accurate voluntary report.” This gives us an empirical “index” of consciousness to start with. In the history of sensory perception, accurate report has been immensely fruitful, beginning with Newton’s prism experiments and still in wide use today.

The scientific study of color perception would have been impossible without accurate, and voluntary reports. In practice, clinical examinations of vision and hearing still rely on accurate, voluntary report, under optimal reporting conditions.

Like other words in natural language, “consciousness” has several meanings.

It is used in biomedical science to refer to the state of waking consciousness, as assessed by patient responsiveness to questions, commands, and mild pain, scalp EEG, and the ability to describe current events.

Confusingly, the word “consciousness” is also used to refer to the “dimension of conscious vs. unconscious brain events” — that is, as an experimental variable that allows us to study brain differences attributable to “consciousness.”

• This second usage is profoundly different from the first, since it implies a measurable dimension of variation.

• But “consciousness as an empirical variable” is still commonly confused with the waking state, or with subjectivity.

Finally, we use “consciousness of something” to refer to the specific contents of mental life, what we will call “conscious cognitions.” Since the domain of conscious contents is vast indeed, it is crucial to distinguish these meanings from each other.

Our basic operational definition of consciousness is “accurate voluntary report” of a sensory stimulus.

All of your electronic sensory gadgets were engineered according to two centuries of science in the study of sensory consciousness, so we know a great deal about it.

In science, operational definitions use the simplest and most reliable observations that capture the phenomenon of interest.

Conscious experiences go beyond sensory events. Contents of consciousness include —

• Perceptual stimuli

• Inner speech

• Reportable dreams and visual imagery

• The fleeting present and its fading traces in immediate memory

• Interoceptive feelings like pleasure, pain, and excitement

• The exteroceptive body senses, including touch and pain

• Reportable emotions

• Autobiographical events as they are experienced and recalled

• Clear and immediate intentions

• Expectations and effortful voluntary control

• Explicit beliefs about oneself and the world

• Reportable feelings of knowing (FOKs)

• Novel skills as opposed to over-practiced ones

• Concepts that are abstract but still reportable

This basic list has not changed since Aristotle, and it may be a cultural universal. Scientifically it is crucial to focus on precise experimental comparisons between cognitions that are conscious and those that are not.

Table 1. There Are Many Ways To Compare Closely Similar Conscious And Unconscious Brain Events.

In recent decades the relationships between the conscious brain state and its reportable contents has received a great deal of clarification. We know much less about the spontaneous stream of consciousness, even though we are making rapid progress. Currently, a very high tech version of the electrical activity of the electromagnetic radiation around the head, called the electroencephalogram (EEG), is among our very best tools for studying the conscious brain.

In science, operational definitions grow over time from very basic ones, like the ability to describe a sound or a sight to much more sophisticated operations like the EEG. The modern study of the conscious brain combines the ancient observations of human behavior with modern technology for observing the brain’s activity.

Key Terms & Definitions

🧩 Short Quiz: “How Do We Begin to Define Consciousness?”

This quiz will help you lock in the key ideas from Mini-Course #3, where we explore how science builds knowledge from the ground up — one careful observation at a time. Ready? Let’s go! 🧠

Question 1

Why don’t scientists begin with a formal definition of consciousness — or any new scientific concept?

• A) Because scientists prefer to avoid difficult questions

• B) Because consciousness is purely a philosophical problem, not a scientific one

• C) Because science works inductively — we build toward definitions through observation, not the other way around

• D) Because consciousness has already been fully defined by neuroscience

✅ Answer: C This is one of the most important — and most misunderstood — points in our mini-course. Science is not a top-down enterprise. We don’t start with perfect theoretical definitions and work downward. Instead, we begin with simple, observable measurements and gradually refine our understanding. It took four centuries to move from Galileo’s water thermometer to the thermodynamic definition of heat. Consciousness is at an earlier stage of that same journey.

Question 2

What was Galileo’s thermometer, and why do we use it as an example?

• A) It was a perfect instrument that gave the final definition of heat

• B) It was a simple early measuring device — a good enough starting point, even without a complete theoretical understanding of heat

• C) It proved that operational definitions are always wrong

• D) It was designed specifically to study consciousness

✅ Answer: B Galileo’s thermometer — a glass tube of water with colored floating jars — could probably only distinguish noon from evening temperatures in Italy. It was crude by modern standards, but it was enough to get started. We use it to illustrate that early operational definitions don’t need to be perfect; they need to be useful. Science improves its tools over time, along with its understanding.

Question 3

What is the basic operational definition of consciousness used in this course?

• A) The ability to dream during sleep

• B) The presence of measurable brain waves on an EEG

• C) Accurate voluntary report of a sensory stimulus

• D) The capacity to store long-term memories

✅ Answer: C “Accurate voluntary report” is the simplest and most reliable starting point for measuring conscious experience scientifically. It has a long and fruitful history — from Newton’s prism experiments to modern clinical hearing and vision tests. It’s not the final word on consciousness, but like Galileo’s thermometer, it’s a solid, workable place to begin.

Question 4

Which of the following is on Baars’ list of conscious experiences — a list he notes has remained essentially unchanged since Aristotle?

• A) Unconscious grammatical processing

• B) Automatic motor skills like riding a bike

• C) Reportable dreams and visual imagery

• D) Subconscious emotional suppression

✅ Answer: C The contents of consciousness are broader than most people assume — they include not just sensory perceptions but also inner speech, bodily feelings, reportable emotions, autobiographical memories, intentions, and yes, dreams and visual imagery. What unites them is that they are all reportable — they can be described accurately under the right conditions. The unconscious processes in the other options, by definition, don’t make that list.

Science doesn't ask you to have all the answers — it asks you to stay curious, keep observing, and refine your understanding over time.

And that's something every one of us can do. 🔬✨

In case you missed them, here are links to Mini-Courses #1 & #2

Footnotes 

There are very important poems and novels in the “stream of consciousness” tradition by authors such as James Joyce and Virginia Woolf.

See Part II, Chapter 1.2 "But what is consciousness" in your copy of "On
Consciousness: Science & Subjectivity" to read and learn more (Baars & Geld, 2019). 

Table 1. There Are Many Ways To Compare Closely Similar Conscious And Unconscious Brain Events. Baars, B. J., and Geld, N. (2019). On Consciousness: Science and Subjectivity: Updated Works on Global Workspace Theory. New York, NY: The Nautilus Press Publishing Group.

What makes an event conscious? A number of influential answers have been proposed. One holds that consciousness depends upon novelty: an event becomes conscious when it violates expectation. Another proposes nearly the reverse: that consciousness depends upon a match between input and memory, such that the event can be recognized and incorporated into experience.

Both proposals capture something important. Neither appears sufficient.

A purely novel event cannot be consciously experienced unless it occurs within some relatively stable background of understanding. If every expectation were violated at once—if an input were wholly new—it could not be consciously grasped as an event at all. Novelty is intelligible only against a framework that is not itself entirely novel.

But the opposite view also fails if taken without qualification. A perfect match between input and expectation leads not to vivid consciousness, but to habituation. When an event becomes wholly predictable, conscious experience tends to fade. What has become fully redundant ceases, in the ordinary case, to claim conscious notice.

This suggests a more plausible conclusion. Conscious experience appears to depend upon some match, but not too much; some mismatch, but not too much. It seems to occupy an intermediate range.

For that reason, the concept of information appears more useful here than either simple match or simple mismatch.

Information rather than simple match or mismatch

Information, in the psychologically relevant sense, involves two features at once. There must be sufficient stability in the interpretive frame for the event to be understood at all. But there must also be sufficient unpredictability in the details for uncertainty to be reduced. Informative input is therefore neither sheer novelty nor mere repetition.

This way of stating the matter has several advantages.

First, it preserves what is valid in the novelty view without making consciousness depend upon mismatch alone. Surprise is certainly one route to consciousness, but surprise may be understood as a special case: a violation not simply of details within a frame, but of the frame by means of which the input had been expected in the first place.

Second, it preserves what is valid in the match view without allowing consciousness to collapse into familiarity. Recognition matters, but complete predictability tends toward redundancy, and redundancy tends toward the loss of conscious salience.

Third, the language of information helps clarify the role of significance. Events that matter to the organism—because they bear upon goals, danger, pain, or action—remain conscious in part because they continue to reduce uncertainty in a broader frame of relevance.

The central point may therefore be put simply: conscious input must be usable input. It must occur within a sufficiently stable frame to be understood, while still contributing something not already assimilated.

Consciousness does not lie at the extremes

The point becomes clearer when the two extremes are considered.

At one end lies total familiarity. When input is perfectly represented in advance, it becomes redundant with respect to its representation. It no longer calls for adaptive work. Under such conditions, consciousness tends to diminish.

At the other end lies total disorganization. When input is too strange, too unframed, or too disruptive of existing interpretation, it cannot yet be experienced coherently as such. Fragments may be registered; puzzlement or disorientation may occur; but a stable conscious experience of the event itself is lacking.

Between these poles lies the region in which consciousness appears most likely: the point at which there is enough structure for understanding, but enough uncertainty to require adaptation.

It is in this intermediate region that informative conscious experience appears to arise.

Some apparent counterexamples

This argument depends in part upon what may be called the redundancy effects: repeated events often lose their conscious vividness. Yet there are familiar cases that seem, at first glance, to challenge this claim.

One class of cases involves highly significant events. Chronic pain, for example, does not simply fade away because it is repeated. Nor do highly unpredictable or consequential events quickly vanish from consciousness. But this need not be treated as a genuine exception. Significance may itself be understood in informational terms: such events continue to reduce uncertainty in a higher-order frame shaped by concern, action, or survival.

Another class of cases involves practice. Practice sometimes seems to increase conscious accessibility rather than diminish it. Memorized material may come to mind more readily with rehearsal. A visual target may begin to “pop out” after repeated search.

But in such cases what becomes automatic is not the conscious content as such. What is practiced is the process of access—the skill of recall, the strategy of search, the learned route into consciousness. The process becomes more automatic; its results may remain informative.

There are also cases in which a repeated stimulus fades, only to reappear under a new interpretation. From an informational point of view, this is not surprising. The same input can become newly informative if the framing context changes. A shift in interpretive frame creates new information, even when the stimulus itself is repetitive.

Such cases therefore do not overturn the general argument. They point, rather, toward a richer understanding of information and adaptation.

A note on the term “information”

The term “information” is used here in a sense close to the classical formulation associated with Shannon, in that it concerns the reduction of uncertainty. But psychological life is not exhausted by simple message channels. Human frames are multidimensional, shifting, and deeply structured by memory, learning, and context.

Still, the central insight remains useful. Conscious experience seems to arise where there is a relatively stable frame of choice within which uncertainty can still be reduced.

That qualification is essential. The frame must be stable enough to support interpretation, but not so fixed that nothing remains to be learned.

Consciousness as a stage of adaptation

This brings the discussion to adaptation.

To adapt to an input is to learn it, to represent it, and to bring it into a form that becomes increasingly predictable. Successful adaptation reduces uncertainty. In the limiting case, it produces redundancy.

From this point of view, conscious experience belongs to a particular stage in the adaptive cycle.

If an event is already fully assimilated, it is too predictable to require consciousness. If it demands a wholesale reorganization of the framing context, it may be too disordered to be consciously experienced in an integrated way. But if it falls between those extremes—if it can be understood within a relatively stable frame while still making adaptive demands—conscious experience becomes possible.

For that reason, informative conscious events may be understood, in a deep sense, as calls for adaptation.

Consciousness is not merely a passive display of what is present. It belongs to an active process by which the nervous system reduces uncertainty, revises expectations, and acquires new predictability without collapsing into either automatism or confusion.

The broader claim

Seen in this light, a number of familiar ideas converge: consciousness, information, uncertainty reduction, significance, learning, adaptation, predictability, and redundancy.

Conscious experience is not best understood as the mere registration of novelty. Nor is it the simple presence of a match between input and memory. It appears instead to mark a special intermediate condition: one in which there is enough order for an event to be grasped, and enough remaining uncertainty for that event to matter.

What is wholly familiar is generally not conscious. What is wholly unintelligible cannot be fully conscious either.

Consciousness appears to arise in between: where input is structured enough to be understood, yet novel enough to be informative.

You are conscious of some aspects of reading right now — but are you aware of the touch of your chair, a faint residual taste, or a conversation drifting in the background? Perhaps not — until just now. That small shift is exactly what this mini-course is about.

We also dip into some nifty natural comparison experiments, plus a short, reflective quiz.

Shall we begin?

You are conscious, and so am I.

This much we can tell pretty easily, since when we are not conscious our bodies wilt, our eyes roll up into their orbits, our brain waves become large, slow, and regular, and we cannot read a sentence like this one.

While the outer signs of consciousness are pretty clear, it is our inner life that counts for most of us.

The contents of consciousness include

• the immediate perceptual world;

• inner speech and visual imagery;

• the fleeting present and its fading traces in immediate memory;

• bodily feelings like pleasure, pain, and excitement;

• surges of feeling; autobiographical events when they are remembered;

• clear and immediate intentions, expectations and actions;

• explicit beliefs about oneself and the world;

• and concepts that are abstract but focal.

In spite of decades of behavioristic avoidance, few would quarrel with this list today.

At this instant you and I are conscious of some aspects of the act of reading —the shape of these letters against the white texture of this page, and the inner sound of these words. But we are probably not aware of the touch of your chair, of a faint residual taste, the subtle balancing of our body against gravity, a flow of conversation in the background, or the delicately guided eye fixations needed to see this phrase; nor are we now aware of the fleeting present of only a few seconds ago, of our affection for a friend, and some of our top life goals.

These unconscious elements are as important as the conscious ones, because they give us natural comparison conditions.

For example: While you are conscious of words in your visual focus, you surely did not consciously label the word focus just now as a noun; yet this sentence would be incomprehensible if highly specialized language analyzers — located in the cortex of the brain, (touch just above your left ear) — did not treat “focus” as a noun unconsciously.

The meaning would change significantly if you understood it to be a verb or an adjective. It is revealing to compare these conscious and unconscious aspects of the same word.

On reading focus, you were surely unaware of its nine alternative meanings, though in a different sentence you would instantly bring a different meaning to mind. What happened to the others?

A wealth of evidence supports the notion that some of those meanings existed unconsciously for a few tenths of a second before your brain decided on the right one. Most words have multiple meanings, but only one at a time can become conscious. This seems to be a fundamental fact about consciousness.

These examples illustrate the sense of the word consciousness we aim to understand — that is, focal consciousness of easily described events, like I see a printed page, or He imagined his mother’s face. A great body of evidence shows that conscious contents like this can be reported as conscious with great accuracy under the right conditions.

These conditions include

• immediate report,

• freedom from distraction,

• and some way for the outside observer to verify the report.

These are standard laboratory conditions that apply to thousands of experiments in perception, memory, attention and mental imagery. They also fit the demonstrations presented here.

The meaning of consciousness intended here is best illustrated by your own experience.

Verifiable public report is the key to scientific evidence, but your experience here and now is quite a good index to it. All of the subjective demonstrations used here can be tested objectively, and all the objective facts can be experienced by you and me.

That is why we believe we can talk about consciousness as such.

When a scattered group of scientists began to return to consciousness in the early 1980s (see how recent this was?), the topic was not popular. Psychologists and brain scientists will remember a time when consciousness was essentially taboo thanks to the dominance of philosophical behaviorism.

Yet in the 25 centuries before 1900, the study of mental life was a central topic for thoughtful people in many, many cultures. For Plato, Aristotle, Lao Tzu, Gautama Buddha, and the Vedantists, it was a plain truth that all of us are conscious.

Consciousness and attention

“My experience is those things I agree to attend to, those items I notice shape my mind ⎯ without selective interest, experience is an utter chaos.

Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.

Focalization, concentration of consciousness are its essence.”

~ William James, The Principles of Psychology (1890)

For more than a hundred years scientists have used William James’s definition of attention. It is routinely cited in scientific writings on attention, and yet, we have not read James’s definition as carefully as we should have. The words that are often overlooked are in italics.

Consciousness refers to reportable experiences, and attention involves voluntary access to consciousness.

For William James, attention is not the same as consciousness; rather, attention involves selecting one conscious experience rather than another. Our sense of self is deeply tied to where we direct our attention. By consciously choosing where to focus, we shape our reality, our thoughts, and ultimately, our identity.

We turn the dial to a football game on television in order to experience it consciously. Tuning in the game is a selective act: watching it is the resulting conscious experience. English makes a clear distinction between “looking” versus “seeing,” “listening” versus “hearing,” “touching” versus “feeling,” and maybe even “sniffing” versus “smelling.” The first word of each pair imparts a sense of selection, while the second describes the resulting conscious experience.

Attention and consciousness are not the same, but they are deeply intertwined.

Attention selects information, but consciousness integrates it into a meaningful whole.

Focus is powerful because it filters chaos into clarity. Conscious awareness is not everything, but it’s where the most meaningful decisions happen. Consciousness is the ‘stage’ on which our sensations, perceptions, thoughts, and feelings play to a vast, mostly silent audience.

The spotlight metaphor comes in handy here. In the dark theater we cannot see who controls the spotlight or what decisions guide its movements, all that is hidden in darkness. We only experience the results of those decisions. From that point of view attention is not something we normally experience.

Consciousness is a fundamental question, like mass and energy, entropy and life.

Scientists can’t avoid it, so we use any number of pseudonyms. People call it “perception” or “attention” or even “knowledge.” Those terms capture part of the truth, but they are by no means the whole explanatory network. Empirical anchors are emerging even today, with some real progress on cortical markers for conscious events that are comparable to experimentally matched unconscious ones. This is an emerging field, but it is being developed in a very reliable way by excellent researchers.

Consciousness is a part of nature, and we now have clear evidence about the “organ of the conscious mind,” the cerebral cortex, which fills 80 percent of the cranial volume. Broadly, sensory perception is conscious, while “stored memory traces” are not. Endogenous senses like inner speech and visual imagery are also conscious, perhaps more vividly in children.

The most revealing studies compare matched conscious and unconscious conditions, aka “contrastive analysis,” and that has allowed us to pinpoint the location and processes that give rise to visual consciousness, for instance. The conditions that are compared include waking vs. sleep, waking vs. coma, but, also, conscious and unconscious events within the waking state.

Right now, you are conscious of the words you see, but there are many, many unconscious processes happening at the same time to help you understand the grammar of this sentence. So we always compare something that is conscious to something that is not. This whole body of evidence is also transforming the study of “disorders of consciousness” in medicine.

Understanding consciousness is not just a scientific challenge; it is a key to understanding what it means to be human.

In these Mini-Courses, we highlight some of the evidence about the conscious brain. Consciousness is a fundamental scientific question. Elucidating its biological and psychological bases could therefore pave the way for major breakthroughs in basic science and clinical medicine.

Such an understanding would have profound implications for philosophy, and for understanding your own inner life and behavior. The mind thrives on curiosity.

🧩 Short Quiz: "How Your Inner World Truly Matters"

Attention is not the same as consciousness. Your brain is processing far more than it ever brings into focus — and understanding that gap is one of the most fascinating discoveries in modern neuroscience. This short quiz will help you lock in the key ideas from Mini-Course #2. No pressure — just curiosity! 👁️

Question 1

According to William James, what is the relationship between attention and consciousness?

• A) They are exactly the same thing

• B) Attention selects one conscious experience over another — they are related but not identical

• C) Consciousness controls attention, but not the other way around

• D) Attention only operates during sleep

✅ Answer: B James was careful to distinguish the two. Attention is the voluntary, selective act — like turning the dial to a TV channel. Consciousness is the resulting experience of actually watching the program. You choose where to look; consciousness is what you see when you get there.

Question 2

When you read the word focus, your brain unconsciously considered multiple meanings before settling on one. What does this reveal?

• A) That most people are poor readers

• B) That unconscious processes are unreliable

• C) That only one meaning of a word can be conscious at a time — a fundamental fact about consciousness

• D) That language is processed entirely consciously

✅ Answer: C In the fraction of a second it takes to read a word, your brain silently auditions all its possible meanings — then presents just one to your conscious mind. You never experience the competition. This is a vivid example of how much cognitive work happens entirely outside your awareness, every moment of every day.

Question 3

James uses the pairs looking/seeing and listening/hearing to make a point. What is he illustrating?

• A) That our senses are often unreliable

• B) That the first word in each pair describes a selective act, while the second describes the resulting conscious experience

• C) That sight and hearing are more important than other senses

• D) That unconscious attention is more powerful than conscious attention

✅ Answer: B This elegant distinction is hiding in plain sight in everyday English. “Looking” implies intention and selection — you are directing your attention. “Seeing” is what happens as a result. The same logic applies to listening/hearing and touching/feeling. Attention is the action; consciousness is the reward.

How did you do? Whether you aced it or found surprises along the way, that sense of discovery is your inner world at work — and that's exactly the point. 🧠✨

• In case you missed it, here’s Mini-Course #1: Your Stream of Consciousness 🕊️

There is a familiar fact about conscious experience that deserves more emphasis than it usually receives. A repeated stimulus tends to fade from awareness, even though its physical presence may remain essentially unchanged. The pressure of a chair, the hum of a room, the stable illumination of a page, and countless other ongoing features of the perceptual world may continue to stimulate the senses while becoming progressively less conscious.

This simple fact is not trivial. It suggests that conscious experience is not a direct function of physical stimulation alone.

The point may be put more precisely. The same physical stimulus may exist under two different conditions. In the first case it is relatively novel, informative, and conscious. In the second, after repetition or habituation, it may become far less conscious, although the physical input itself remains much the same. If so, the determining factor cannot lie in stimulation as such. Something else must be involved.

One useful candidate is information.

I shall use that term here in its conventional sense as a reduction of uncertainty within a set of possible alternatives. Information in this sense always presupposes some frame within which alternatives are defined.

A signal can only be informative if it reduces uncertainty among available possibilities. This is the familiar conception derived from information theory, though I shall use it here in a broader and more qualitative psychological sense.

The value of that conception is that it helps make sense of a fact that is otherwise rather puzzling: consciousness seems closely related to the informativeness of an event. What is novel tends to become conscious. What is significant tends to become conscious. What violates expectation tends to become conscious. Even the absence of an expected event may become conscious when it is informative in the relevant frame. By contrast, what is fully predictable tends to become redundant, and therefore less conscious.

Repetition, considered as a physical fact, is not the same as redundancy, considered in psychological terms.

The same physical energy impinging upon the same receptors may be either informative or redundant, depending upon the reduction of uncertainty in the relevant frame. A repeated event may remain informative if it still resolves some uncertainty. By contrast, even a continuing stimulus may become redundant if it no longer makes any difference within the prevailing context of expectation.

Sometimes this can be shown very simply. A missing item in a sentence may become more conscious than the words that are physically present. An omitted expected sound may attract more awareness than the ongoing background of sounds that continues without interruption. Thus the presence of stimulation and the informativeness of an event are not identical. They can vary independently. This is one reason it is useful to distinguish between physical stimulation and real information.

The distinction becomes especially clear when one considers significance.

A stimulus may carry information not only because of its sensory properties, but because it suggests something beyond itself. In Pavlov’s experiments, for example, the bell was not merely a sound. It became significant because it signaled food. That significance was not exhausted by its local acoustic character. It reduced uncertainty within a wider frame defined by the animal’s condition, expectations, and purposes. Under those circumstances the bell became more informative, and for that reason it also tended to remain conscious longer and to habituate more slowly.

This suggests that information may exist at different levels.

A stimulus may have one kind of information value within a narrow sensory frame, and another within a broader frame of action, expectation, or biological significance. What matters to an organism is not simply that stimulation occurs, but what that stimulation means within an organized situation.

That phrase deserves emphasis. Consciousness does not seem to accompany sheer disorder. Nor does it seem to accompany what is wholly predictable. Rather, conscious contents appear most naturally when there is both a stable context and some remaining degree of freedom within it. We become conscious of an event when it occurs within an organized frame and at the same time resolves some live uncertainty inside that frame. When no such uncertainty remains, the event tends to recede from awareness.

This way of viewing the matter helps illuminate a number of familiar phenomena. Stimulus habituation is perhaps the clearest example.

• A repeated sound, touch, or visual pattern tends to become less conscious over time.

• Practiced skills likewise become less conscious as they become automatic.

• Semantic satiation, perceptual adaptation, and the fading of stable contextual features into the unnoticed background of ordinary life all seem to belong to the same family of cases.

In each of these, what was initially conscious becomes progressively less so as it becomes more redundant.

These are not minor curiosities. They suggest a rather direct relationship between conscious experience and the informativeness of an event.

One of the strongest indications of this relationship lies in what may be called redundancy effects. Redundancy, in information theory, is the transmission of a signal after the relevant uncertainty has already been reduced to zero. Something similar seems to hold in conscious experience. Once an event has become fully expected within the relevant frame, its continued occurrence carries little or no new information. It may remain true. It may continue to provide a useful background for interpretation. But it no longer demands conscious attention in the same way.

That point is worth stressing, because redundancy does not imply falsehood. It implies only a loss of informativeness.

Much of what structures conscious experience may therefore become relatively unconscious precisely because it has become well established. Learned contextual systems, routine conceptual presuppositions, stable features of the local environment, and other predictable aspects of the world may continue to shape ongoing interpretation without becoming conscious in their own right. They do not disappear. They simply recede into the background.

Yet if that is true, some representation of the expected event must continue to exist. Otherwise mismatches could not be detected. If a habituated stimulus suddenly changes, the discrepancy can once again evoke orienting and awareness.

This suggests that the representation of a repeated event may continue after habituation, but in a form that is not normally conscious.

What changes is not necessarily the existence of a representation, but its information value for consciousness.

We may therefore contrast two cases under nearly identical physical conditions: first, the occurrence of a stimulus when it is relatively novel and informative; and second, its later recurrence after it has become redundant. In the first case it is more likely to become conscious. In the second, less so. The difference lies not primarily in the physical stimulus itself, but in the degree to which it reduces uncertainty within the relevant frame.

If this line of argument is correct, it points to a general conclusion.

Consciousness is not simply a passive accompaniment of sensory input. It appears instead to be especially sensitive to events that are novel, significant, unexpected, or otherwise capable of reducing uncertainty within an organized context.

That, at least, is the central suggestion.

Repeated stimulation fades from awareness not because stimulation has ceased, but because what was once informative has become redundant. What tends to enter consciousness most readily is not bare input, but input that makes a difference within a stable frame of expectation, action, and significance.

Conscious experience, in short, appears to be informative.

Read more

What is your mind doing right now — and what was it doing just before you read this?

One of the interesting things about consciousness is that it appears as a stream of information,

of visual information, of auditory information, of feelings, of touch, of inner feelings of emotions, and of a number of other things that were very well studied by novelists and poets for hundreds of years. And summarized by William James in 1890 as the Stream of Consciousness (SoC), which he called a little river in a broad meadow.

Another metaphor he used was to talk about the apparently arbitrary “flights and perches” of conscious ideas, so that you have one idea, and then if you’re very relaxed or if you’re half drowsy, something else will come to mind that seems to be totally unrelated. So you’re jumping around in a sort of a disorganized fashion in this Stream of Consciousness, and very many novelists, movie makers, and other creative people have used the Stream of Consciousness states, these half drowsy states to come up with creative, really wonderfully creative ideas.

Stream of Consciousness is a very creative state, but it’s not a highly organized state, like we need in order to study science. In science, we need to be very systematic, very coherent, very logical, and very sensitive to evidence. Science is very disciplined.

We all have a Stream of Consciousness.

Stream of Consciousness, the way novelists and poets have used it for centuries, is a very creative thing.1 The metaphor of bird “flights and perches” — the bird is flying rapidly from one place to another in the trees, and “perches” are these momentary stops that birds make in order to look around, maybe in order to orient themselves and find out where the other birds are located. These “flights and perches” are a famous metaphor for the stream of consciousness coming from William James. It’s a very interesting thing to do as a personal experiment.

Very often we don’t pay much attention to our Stream of Consciousness, but it’s easy to do that. And it’s also very interesting to do that, because it turns out from the science we have on it, that the things that we are the most interested in — the fights that we just had with our friends, the beauty of a person that we’re attracted to — those kinds of things, that the things that we normally don’t talk much about seem to dominate these spontaneous Stream of Consciousness. And then we have these strange experiences when we’re getting drowsy that are sort of dreamlike, and very, very creative.

It’s a very interesting topic that has been studied to some extent. And, of course, consciousness is a function of the cerebral cortex, which is where we can tie it into brain anatomy.

The Stream of Consciousness (SoC) is constantly active, even when we are awake but physically passive.

Consciousness has largely been perceived as a passive state. When scientists started to use fMRI to measure metabolic “hot spots” in the brain, the collection of brain regions which were active in the absence of a focal task were considered to be “the brain’s metabolic baseline”, known as the “default mode network” (DMN). This notion, however, has received plenty of pushback in recent years, and this baseline is now regarded as an active cognitive process. Some scientists argue that the DMN is a spontaneous stream of consciousness, which we can observe in ourselves.

• The DMN is a network of interacting brain regions that is active when a person is not focused on a task, and the brain is at wakeful rest such as during daydreaming and spontaneous thought, and is measurable with fMRI.

• The DMN is also active when we are thinking about other people, about ourselves, and about our past and future.

Conscious events go beyond the senses, including numerous conscious experiences, such as feelings of effort (like thinking of 3 words for effort), interoceptive emotional feelings, conscious beliefs and ideas, internal visual imagery, and inner speech.

• As discussed earlier, the SoC is the apparently spontaneous “flights” and “perches” of conscious ideas, in the words of William James.

• The SoC is explained in Global Workspace Theory as an ongoing interplay between conscious contents and unconscious frames, especially goal frames in the process of solving spontaneously posed questions.

All of the sensory, cognitive, social and emotional sciences are relevant to understanding both conscious and unconscious mind-brain events. The most persuasive evidence, perhaps, comes from Conscious vs. Unconscious comparisons, where we study a conscious sensory stream (for example) and compare it to a simultaneous unconscious stream.

The Rich Tradition of Stream of Consciousness in the Arts

Anyone truly interested in consciousness should be aware of the rich tradition of “stream of consciousness” novels and poetry, including Marcel Proust, James Joyce, Gertrude Stein and Virginia Woolf.

It continues to influence the arts today. Here is just a fragment from Proust's "Remembrance of Times Past, Vol 1: Swann’s Way" (1913). Waking up in the middle of the night, the narrator tells:

Stream of consciousness novelists often acknowledged their debt to William James’ Principles of Psychology (1890), which first proposed the term “stream of thought” to describe the somewhat helter-skelter flow of thoughts we seem to experience in everyday life.

William James spent a lifetime discussing these matters with his brother Henry, one of the great pioneers of the psychological novel.

Thus the literary and psychological understanding of consciousness co-evolved in the 19th century; they were inseparable, and only split apart after 1900, creating a gap between the sciences and the arts. With the scientific return to consciousness we may see a healing of that divide.

William James on the Stream of Consciousness

“Consciousness, then, does not appear to itself chopped up in bits

[...] A 'river' or a 'stream' are the metaphors by which it is most naturally described. In talking of it hereafter, let us call it the stream of thought, of consciousness, or of subjective life. [...]

As we take, in fact, a general view of the wonderful stream of our consciousness, what strikes us first is this different pace of its parts. Like a bird's life, it seems to be made of an alternation of flights and perchings. The rhythm of language expresses this, where every thought is expressed in a sentence, and every sentence closed by a period.

The resting-places are usually occupied by sensorial imaginations of some sort, whose peculiarity is that they can be held before the mind for an indefinite time, and contemplated without changing; the places of flight are filled with thoughts of relations, static or dynamic, that for the most part obtain between the matters contemplated in the periods of comparative rest.

Let us call the resting-places the 'substantive parts,' and the places of flight the 'transitive parts,' of the stream of thought. [...]

Once more take a look at the brain. We believe the brain to be an organ whose internal equilibrium is always in a state of change, - the change affecting every part. As the brain-changes are continuous, so do all these consciousnesses melt into each other like dissolving views. Properly they are but one protracted consciousness, one unbroken stream.”

— William James (1890) The Principles of Psychology, Chapter IX. The Stream of Thought, 2) Thought is in Constant Change; 3)Within each personal consciousness, thought is sensibly continuous.

Enrichment Activity 📝

If you would like to consider some of your personal experiences of your stream of consciousness, it will help to clarify the points in this lesson. This is where consciousness science begins — not in the lab, but in your own awareness.

• It sometimes helps to write your thoughts down, or audio record them, and perhaps to revisit them later. Notice any patterns?

• If you have favorite moments in a piece of music, or in a poem, strange imagery at the edge of sleep, or anything else, something that you like very much, that can also help to expand your understanding of this subject.

There is so much we can learn from our own stream of consciousness.

Introducing: Consciousness & the Brain Mini-Courses

Short. Focused. Narrated and hosted by yours truly. Some of the world’s leading consciousness researchers will join us, too.

These are not lectures. They are guided explorations, roundtables, one-on-one talks, and open-minded discussions — designed to take a single idea from the frontier of neuroscience and make it vivid, personal, and unforgettable.

I’m Bernard Baars, and I’ll be narrating or hosting every lesson. Each mini-course is produced by , my creative collaborator of over ten years — together we’ve been translating the science of the conscious mind and brain into published articles, books, podcasts, seminars, events, workshops, and communication that actually reaches people.

How it works:

🔓 Select mini-courses are free for all subscribers

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Whether you’re a neuroscientist, an artist, a student, or someone who has ever wondered what it means to be conscious — there is something here for you.

We read every comment. Share your thoughts below, we’re listening — community is part of how we learn too.🧠

Q. How does consciousness, in the way you discuss it, relate to working memory?

A. Bernard Baars

Very good question!

So, working memory is operationally somewhat different from reporting conscious events directly. But not much different. They are both part of the central limited capacity system, which is itself a great puzzle. But we know, of course, by now from cortical studies that Broca’s area, for example, is heavily involved with inner speech, which is one of the central components of working memory.

It is useful to make the distinction between the things we know consciously directly and the things such as inner speech, which have a significant unconscious component also.

And I don’t give chicken or egg answers, I think it’s both the chicken and the egg, both working memory and consciousness.