Alexandre Lim

IncognitoBy David Eagleman

The human brain is probably the most mysterious, complex, and fascinating organ. We're not who we think we are. It's scary to learn how little we are truly in control. You'll come changed after reading this book. Incognito was a pleasure to read.


The state of the physical material determines the state of the thoughts.

Most of what we do and think, and feel is not under our conscious control.

Your consciousness is like a tiny stowaway on a transatlantic steamship, taking credit for the journey without acknowledging the massive engineering underfoot.

Brains are in the business of gathering information and steering behavior appropriately.

Consciousness is the smallest player in the operations of the brain. Our brains run mostly on autopilot, and the conscious mind has little access to the giant and mysterious factory that runs below it.

Consciousness developed because it was advantageous but advantageous only in limited amounts.

The brain works its machinations in secret, conjuring ideas like tremendous magic. It does not allow its colossal operating system to be probed by conscious cognition. The brain runs its show incognito.

As Carl Jung put it, “In each of us, there is another whom we do not know.”

So consciousness is best left uninvited from most of the parties. When it does get included, it’s usually the last one to hear the information.

One does not need to be consciously aware to perform sophisticated motor acts.

The conscious mind is not at the center of the action in the brain; instead, it is far out on a distant edge, hearing but whispers of the activity.

We are astoundingly poor observers. And our introspection is useless on these issues: we believe we’re seeing the world just fine until it’s called to our attention that we’re not.

In many of these cases, the eyes are in the right place, but the brain isn’t seeing the stimuli. Vision is more than looking.

The brain doesn’t need a full model of the world because it merely needs to figure out, on the fly, where to look and when.

The brain generally does not need to know most things; it merely knows how to go out and retrieve the data. It computes on a need-to-know basis.

Brains reach out into the world and actively extract the type of information they need.

A physicist thinks about motion as a change in position through time. But the brain has its own logic, which is why thinking about motion like a physicist rather than a neuroscientist will lead to wrong predictions about how people operate.

To the brain, it doesn’t matter where those pulses come from—from the eyes, the ears, or somewhere else entirely. As long as they consistently correlate with your own movements as you push, thump, and kick things, your brain can construct the direct perception we call vision.

The apparatus reminds us that we see not with our eyes but rather with our brains.

At least 15 percent of human females possess a genetic mutation that gives them an extra (fourth) type of color photoreceptor—and this allows them to discriminate between colors that look identical to the majority of us with a mere three types of color photoreceptors.

The deep secret of the brain is that not only the spinal cord but the entire central nervous system works this way: internally generated activity is modulated by sensory input.

The whole system looks a lot more like a marketplace than an assembly line.

The brain internally simulates what will happen if you were to perform some action under specific conditions. Internal models not only play a role in motor acts (such as catching or dodging) but also underlie conscious perception.

The brain refines its world model by paying attention to its mistakes.

Awareness of your surroundings occurs only when sensory inputs violate expectations.

It is not only vision and hearing that are constructions of the brain. The perception of time is also a construction.

Our sense of time—how much time passed and what happened when—is constructed by our brains. And this sense is easily manipulated, just like our vision can be.

So the first lesson about trusting your senses is: don’t. Just because you believe something to be true, just because you know it’s true, that doesn’t mean it is true.

The ability to remember motor acts like changing lanes is called procedural memory, and it is a type of implicit memory—meaning that your brain holds the knowledge of something that your mind cannot explicitly access.

There can be a large gap between knowledge and awareness. When we examine skills that are not amenable to introspection, the first surprise is that implicit memory is completely separable from explicit memory: you can damage one without hurting the other.

The results can be troubling. The reaction times of subjects are faster when the pairings have a strong association unconsciously.

People tend to love reflections of themselves in others.

The power of implicit egotism goes beyond your name to other arbitrary features of yourself, such as your birthday.

We are influenced by drives to which we have little access and which we would never have believed had not the statistics laid them bare.

Priming underscores the point that implicit memory systems are fundamentally separate from explicit memory systems: even when the second one has lost the data, the former one has a lock on it.

This is known as the mere exposure effect, and it illustrates the worrisome fact that your implicit memory influences your interpretation of the world—which things you like, don’t like, and so on.

Another real-world manifestation of implicit memory is known as the illusion-of-truth effect: you are more likely to believe that a statement is true if you have heard it before—whether or not it is actually true.

And the information was being delivered in the form of a “hunch”: subjects began to choose the good decks even before they could consciously say why.

The gut feeling was essential for advantageous decision-making.

In this view, physical states of the body provide the hunches that can steer behavior.

If you cannot always elicit a straight answer from the unconscious brain, how can you access its knowledge? Sometimes the trick is merely to probe what your gut is telling you.

Conscious parts of the brain train other parts of the neural machinery, establishing the goals and allocating the resources.

Consciousness is the long-term planner, the company's CEO, while most of the day-to-day operations are run by all those parts of her brain to which she has no access.

Consciousness tends to interfere with most tasks—but it can be helpful when setting goals and training the robot.

The more things get automatized, the less conscious access we have.

The brain’s circuits are designed to generate behavior that is appropriate to our survival.

Synesthesia is a fusion of different sensory perceptions.

Instead of reality being passively recorded by the brain, it is actively constructed by it.

While neuroscientists study the pieces and parts that make up brains, evolutionary psychologists study the software that solves social problems.

Infants make assumptions about the intentions of adults. If an adult tries to demonstrate how to do something, a baby will impersonate him. But if the adult appears to mess up the demonstration (perhaps punctuated with a “Whoops!”) the infant will not try to impersonate what she saw but instead what she believes the adult intended.

The brain cares about social interaction so much that it has evolved special programs devoted to it: primitive functions to deal with issues of entitlement and obligation. In other words, your psychology has evolved to solve social problems such as detecting cheaters—but not to be smart and logical in general.

Instincts differ from our automatized behaviors (typing, bicycle riding, serving a tennis ball) in that we didn’t have to learn them in our lifetime. We inherited them. Our innate behaviors represent ideas so useful that they became encoded into the tiny, cryptic language of DNA. This was accomplished by natural selection over millions of years: those who possessed instincts that favored survival and reproduction tended to multiply.

These programs are inaccessible to us not because they are unimportant but because they’re critical. Conscious meddling would do nothing to improve them.

The more obvious and effortless something seems, the more we need to suspect that it seems that way only because of the massive circuitry living behind it.

The large eyes and round faces of babies look cute to us not because they possess a natural “cuteness” but because of the evolutionary importance of adults taking care of babies.

The missing factor in Minsky’s theory was competition among experts who all believe they know the right way to solve the problem. Just like a good drama, the human brain runs on conflict.

Brains can be of two minds, and often many more. We don’t know whether to turn toward the cake or away from it because several little sets of hands are on the steering wheel of our behavior.

I propose that the brain is best understood as a team of rivals.

Paul MacLean suggested that the brain is made of three layers representing successive stages of evolutionary development: the reptilian brain (involved in survival behaviors), the limbic system (involved in emotions), and the neocortex (used in higher-order thinking).

The rational system is the one that cares about the analysis of things in the outside world, while the emotional system monitors the internal state and worries whether things will be good or bad. As a rough guide, rational cognition involves external events, while emotion involves your internal state.

Choices about the priority of actions are determined by our internal states.

Because both the neural systems battle to control the single output channel of behavior, emotions can tip the balance of decision making.

The emotional and rational networks battle not only over immediate moral decisions but also in another familiar situation: how we behave in time.

It’s because people “discount” the future, an economic term meaning that rewards closer to now are valued more highly than rewards in the distant future.

Bubbles are primarily social phenomena; until we understand and address the psychology that fuels them, they’re going to keep forming.

So when we talk about a virtuous person, we do not necessarily mean someone who is not tempted but, instead, someone who can resist that temptation.

Why don’t people take control of their own behavior and enjoy the opportunities of commanding their own capital?

The amazing consequence is that minds can negotiate with different time points of themselves.

The rule of thumb is this: when you cannot rely on your own rational systems, borrow someone else’s.

The conviction that memory is one thing is an illusion.

Biology rarely rests on a single solution. Instead, it tends to reinvent solutions ceaselessly. But why endlessly innovate—why not find a good solution and move on?

As a result of staying mentally vigorous, they built what neuropsychologists call cognitive reserve. It’s not that cognitively fit people don’t get Alzheimer’s; it’s that their brains have protection against the symptoms.

Cognitive reserve—and robustness in general—is achieved by blanketing a problem with overlapping solutions.

Blindsight teaches us that when conscious vision is lost, there are still subcortical factory workers behind the scenes running their normal programs.

Both scientists and laypeople can find themselves seduced into the easy trap of wanting to assign each brain function to a specific location.

This Stroop interference unmasks the clash between the strong, involuntary, and automatic impulse to read the word and the unusual, deliberate, and effortful task demand to state the color of the print.

When one part of the brain makes a choice, other parts can quickly invent a story to explain why.

Hidden programs drive actions, and the left hemisphere makes justifications.

Both parties fatigue to the point of attrition, and the original issue being fought over is finally dumped. The patient will conclude nothing about the situation.

Keeping the union together and making a good narrative does not happen for free—the brain works around the clock to stitch together a pattern of logic to our daily lives: what just happened, and what was my role in it? Fabrication of stories is one of the key businesses in which our brains engage. Brains do this with the single-minded goal of getting the multifaceted actions of the democracy to make sense.

The brain’s storytelling powers kick into gear only when things are conflicting or difficult to understand, as for the split-brain patients or anosognosics like Justice Douglas.

Minds seek patterns.

When everything is going according to the needs and skills of your zombie systems, you are not consciously aware of most of what’s in front of you; when suddenly they cannot handle the task, you become consciously aware of the problem.

Although the ability to be flexible sounds better, it does not come for free—the trade-off is a burden of lengthy childrearing. To be flexible like an adult human requires years of helplessness as an infant. Human mothers typically bear only one child at a time and have to provide a period of care that is unheard-of (and impracticable) in the rest of the animal kingdom.

So are other animals conscious? Science currently has no meaningful way to make a measurement to answer that question—but I offer two intuitions. First, consciousness is probably not an allor-nothing quality but comes in degrees. Second, I suggest that an animal’s degree of consciousness will parallel its intellectual flexibility.

I propose that a useful index of consciousness is the capacity to successfully mediate conflicting zombie systems.

Venting a secret is usually done for its own sake, not as an invitation for advice. If the listener spots an obvious solution to some problem revealed by the secret and makes the mistake of suggesting it, this will frustrate the teller—all she really wanted was to tell. The act of telling a secret can itself be the solution.

Human programmers approach a problem by assuming there’s a best way to solve it or that there’s a way the robot should solve it. But the main lesson we can extract from biology is that it’s better to cultivate a team of populations that attack the problem in different, overlapping manners.

A team-of-rivals brain can naturally harbor both racist and nonracist feelings.

If the conscious you have less control over the mental machinery than we previously intuited, what does all this mean for responsibility?

To what extent is someone at fault if his brain is damaged in ways about which he has no choice? After all, we are not independent of our biology, right?

When your biology changes, so can your decision-making, appetites, and desires.

A slight change in brain chemistry balance can cause large changes in behavior. The behavior of the patient cannot be separated from his biology.

Many of us like to believe that all adults possess the same capacity to make sound choices. It’s a nice idea, but it’s wrong. People’s brains can be vastly different—influenced not only by genetics but by the environments in which they grew up.

Your brains are different; you don’t fit in his shoes. Even if you would like to imagine what it’s like to be him, you won’t be very good at it.

We are not the ones driving the boat of our behavior, at least not nearly as much as we believe. Who we are runs well below the surface of our conscious access.

The complex interactions of genes and environment mean that the citizens of our society possess different perspectives, dissimilar personalities, and varied capacities for decision making. These are not free-will choices of the citizens; these are the hands of cards we’re dealt.

How exactly should we assign culpability to people for their varied behavior when it is difficult to argue that the choice was ever really available?

Sophisticated action can occur without free wills, like homicidal somnambulism.

As with Tourette’s sufferers, those subject to psychogenic disorders, and the split-brain patients, Kenneth’s case illustrates that high-level behaviors can happen in the absence of free will.

The crux of the question is whether all of your actions are fundamentally on autopilot or whether there is some little bit that is “free” to choose, independent of the rules of biology.

So despite all our hopes and intuitions about free will, there is currently no argument that convincingly nails down its existence.

So I’m going to propose what I call the principle of sufficient automatism. The principle arises naturally from the understanding that free will, if it exists, is only a small factor riding on top of enormous automated machinery.

Free will is not as simple as we intuit—and our confusion about it suggests that we cannot meaningfully use it as the basis of punishment decisions.

Let’s put to rest the concern that biological explanations will lead to freeing criminals on the grounds that nothing is their fault. Will we still punish criminals? Yes. Exonerating all criminals is neither the future nor the goal of an improved understanding. Explanation does not equal exculpation. Societies will always need to get bad people off the streets. We will not abandon punishment, but we will refine the way we punish.

The more we discover about the brain's circuitry, the more the answers tip away from accusations of indulgence, lack of motivation, and poor discipline—and move toward the details of biology.

Blameworthiness is the wrong question to ask.

The heart of the problem is that it no longer makes sense to ask, “To what extent was it his biology, and to what extent was it him?” The question no longer makes sense because we now understand those to be the same thing. There is no meaningful distinction between his biology and his decision-making. They are inseparable.

Culpability appears to be the wrong question to ask. Here’s the right question: What do we do, moving forward, with an accused criminal?

The main difference between teenage and adult brains is the development of the frontal lobes.

The goal is to give more control to the neural populations that care about long-term consequences. To inhibit impulsivity. To encourage reflection.

One of the challenges to implementing new rehabilitative approaches is winning popular acceptance. Many people (but not all) have a strong retributive impulse: they want to see punishment, not rehabilitation.

Take xenophobia, the fear of foreigners. It’s completely natural. People prefer people who look and sound like them; although contemptible, it is common to dislike outsiders.

Despite our understanding of the retributive impulse, we agree to resist it as a society because we know that people can get confused about the facts of a crime and that everyone deserves the presumption of innocence until proven guilty before a jury of peers.

This built-in myth of human equality suggests that all people are equally capable of decision making, impulse control, and comprehending consequences. While admirable, the notion is simply not true.

If there is hope of using classical conditioning to effect a change in behavior that would allow social reintegration, then punishment is appropriate.

For those who are modifiable, such as a teenager who still needs further frontal development, a harsh punishment (breaking rocks all summer) would be appropriate. But someone with frontal lobe damage, who will never develop the capacity for socialization, should be incapacitated by the state in a different sort of institution.

The biggest battle I have to fight is the misperception that an improved biological understanding of people’s behaviors and internal differences means we will forgive criminals and no longer take them off the streets. That’s incorrect.

The concept and word to replace blameworthiness is modifiability, a forward-looking term that asks, What can we do from here? Is rehabilitation available? If so, great. If not, will the punishment of a prison sentence modify future behavior? If so, send him to prison. If punishment won’t help, then take the person under state control for the purposes of incapacitation, not retribution.

Neuroscience is just beginning to scratch the surface of questions that were once only in the domain of philosophers and psychologists, questions about how people make decisions and whether they are truly “free.” These are not idle questions but ones that will shape the future of legal theory and the dream of a biologically informed jurisprudence.

There are limits to introspection.

Your most fundamental drives are stitched into the fabric of your neural circuitry, and they are inaccessible to you. You find certain things more attractive than others, and you don’t know why.

The condition of your brain is central to who you are.

We are our brain and its chemicals, and any dialing of the knobs of your neural system changes who you are.

Who you are depends on the sum total of your neurobiology.

Because of inaccessible fluctuations in our biological soup, some days, we find ourselves more irritable, humorous, well-spoken, calm, energized, or clear-thinking. Our internal life and external actions are steered by biological cocktails to which we have neither immediate access nor direct acquaintance.

It is to acknowledge that successive levels of reduction are doomed to tell us very little about the questions important to humans.

Remember what we said earlier about having an 828 percent higher chance of committing a violent crime if you carry the Y chromosome? The statement is factual, but the important question to ask is this: why aren’t all males criminals? That is, only 1 percent of males are incarcerated. What’s going on?

A combination of genetics and environment matters for the final outcome.

If you have certain problems with your brain but are raised in a good home, you might turn out okay. If your brain is fine and your home is terrible, you might still turn out fine. But if you have mild brain damage and end up with bad home life, you’re tossing the dice for a very unlucky synergy.

You inherit a genetic blueprint and are born into a world over which you have no choice throughout your most formative years.

Without a doubt, minds and biology are connected—but not in a manner that we’ll have any hope of understanding with a purely reductionist approach.

Reductionism is not the right viewpoint for everything, and it certainly won’t explain the relationship between the brain and the mind. This is because of a feature known as emergence.

How should we define you? Where do you begin, and where do you end? The only solution is to think about the brain as the densest concentration of youness. It’s the peak of the mountain, but not the whole mountain. When we talk about “the brain” and behavior, this is a shorthand label for something that includes contributions from a much broader sociobiological system.*

Following a one-way street in the direction of the very small is the mistake that reductionists make, and it is the trap we want to avoid.

The future of understanding the mind lies in deciphering the patterns of activity that live on top of the wetware, patterns that are directed both by internal machinations and by interactions from the surrounding world.

Even though few working scientists will design experiments around eccentric hypotheses, ideas always need to be proposed and nurtured as possibilities until evidence weighs in one way or another.

Any neuroscientist who tells you we have the problem cornered with a reductionist approach doesn’t understand the complexity of the problem.

If our brains were simple enough to be understood, we wouldn’t be smart enough to understand them.

Last Updated

July 26th, 2022