How the Mind Works

Steven Pinker
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Pinker weaves together a picture of the human psyche drawing from two big ideas in psychology: the computational theory of mind and the theory of natural selection. This topic is undoubtedly very complex, and if anything, this book shows just how much we don't know yet.

Cognitive science helps us to understand how a mind is possible and what kind of mind we have. Evolutionary biology helps us to understand why we have the kind of mind we have.

The Computational Theory of Mind

Information and computation reside in patterns of data and in relations of logic that are independent of the physical medium that carries them. When you telephone your mother in another city, the message stays the same as it goes from your lips to her ears even as it physically changes its form, from vibrating air, to electricity in a wire, to charges in silicon, to flickering light in a fiber optic cable, to electromagnetic waves, and then back again in reverse order.

In a similar sense, the message stays the same when she repeats it to your father at the other end of the couch after it has changed its form inside her head into a cascade of neurons firing and chemicals diffusing across synapses. Likewise, a given program can run on computers made of vacuum tubes, electromagnetic switches, transistors, integrated circuits, or well-trained pigeons, and it accomplishes the same things for the same reasons.

Natural selection cares only about the long-term fate of entities that replicate, that is, entities that retain a stable identity across many generations of copying.

Intelligence and Information Processing

Intelligence is the ability to attain goals in the face of obstacles by means of decisions based on rational (truth-obeying) rules.

The only reason that humans are smarter than rats is that our networks have more hidden layers between stimulus and response and we live in an environment of other humans who serve as network trainers.

Sentience: subjective experience, phenomenal awareness, raw feels, first-person present tense, “what it is like” to be or do something, if you have to ask you’ll never know.

Information processing requires energy. That is obvious to anyone who has stretched out the battery life of a laptop computer by slowing down the processor and restricting its access to information on the disk. Thinking, too, is expensive. The technique of functional imaging of brain activity (PET and MRI) depends on the fact that working brain tissue calls more blood its way and consumes more glucose. Any intelligent agent incarnated in matter, working in real time, and subject to the laws of thermodynamics must be restricted in its access to information.


A new field of computer science called genetic algorithms has shown that Darwinian selection can create increasingly intelligent software. Genetic algorithms are programs that are duplicated to make multiple copies, though with random mutations that make each one a tiny bit different. All the copies have a go at solving a problem, and the ones that do best are allowed to reproduce to furnish the copies for the next round.

Are we still evolving? Biologically, probably not much. Evolution has no momentum, so we will not turn into the creepy bloat-heads of science fiction. The modern human condition is not conducive to real evolution either. We infest the whole habitable and not-so-habitable earth, migrate at will, and zigzag from lifestyle to lifestyle. This makes us a nebulous, moving target for natural selection. If the species is evolving at all, it is happening too slowly and unpredictably for us to know the direction.

But what about the Darwinian imperative to survive and reproduce? As far as day-to-day behavior is concerned, there is no such imperative. People watch pornography when they could be seeking a mate, forgo food to buy heroin, sell their blood to buy movie tickets (in India), postpone childbearing to climb the corporate ladder, and eat themselves into an early grave. Human vice is proof that biological adaptation is, speaking literally, a thing of the past.

The Minds Eye

To gaze is to think. — Salvador Dali

One can even make an educated guess about the anatomy of mental imagery. The incarnation of a 2½-D sketch in neurons is called a topographically organised cortical map: a patch of cortex in which each neuron responds to contours in one part of the visual field, and in which neighbouring neurons respond to neighbouring parts. The primate brain has at least fifteen of these maps, and in a very real sense they are pictures in the head. Neuroscientists can inject a monkey with a radioactive isotope of glucose while it stares at a bull’s-eye. The glucose is taken up by the active neurons, and one can literally develop the monkey’s brain as if it were a piece of film.


Human reasoning: how people make sense of their world.

Many social psychologists have concluded that the mind is not designed to grasp the laws of probability, even though the laws rule the universe.

Gigerenzer has found that when probabilities are presented as frequencies, people, including specialists, are vastly more accurate at estimating the probability of a disease following a medical test.

Of course, people sometimes reason fallaciously, especially in today’s data deluge. And, of course, everyone should learn probability and statistics.

Geniuses are wonks. The typical genius pays dues for at least ten years before contributing anything of lasting value. (Mozart composed symphonies at eight, but they weren’t very good; his first masterwork came in the twelfth year of his career.)


The key to why we have emotions: an animal cannot pursue all its goals at once.

The biologist George Orians, an expert on the behavioural ecology of birds, recently turned his eye to the behavioural ecology of humans. With Judith Heerwagen, Stephen Kaplan, Rachel Kaplan, and others, he argues that our sense of natural beauty is the mechanism that drove our ancestors into suitable habitats.

Environmental aesthetics is a major factor in our lives. Mood depends on surroundings: think of being in a bus terminal waiting room or a lakeside cottage.

How do we know what can reasonably be attained? A good source of information is what other people have attained. If they can get it, perhaps so can you. Through the ages, observers of the human condition have pointed out the tragedy: people are happy when they feel better off than their neighbours, unhappy when they feel worse off.

People today are safer, healthier, better fed, and longer-lived than at any time in history. Yet we don’t spend our lives walking on air, and presumably our ancestors were not chronically glum.

People do come to feel the same across an astonishing range of good and bad fortunes. But the baseline that people adapt to, on average, is not misery but satisfaction. (The exact baseline differs from person to person and is largely inherited.)

Lottery winners, after their jolt of happiness has subsided, return to their former emotional state. On the brighter side, so do people who have suffered terrible losses, such as paraplegics and survivors of the Holocaust. (see Hedonic treadmill)

The numbers show that it is not the rich, privileged, robust, or good-looking who are happy; it is those who have spouses, friends, religion, and challenging, meaningful work.

How can you be sure that a prospective partner won’t leave the minute it is rational to do so—say, when a 10-out-of-10 moves in next door? One answer is, don’t accept a partner who wanted you for rational reasons to begin with; look for a partner who is committed to staying with you because you are you. Committed by what? Committed by an emotion. An emotion that the person did not decide to have, and so cannot decide not to have.

Family Values

All people today owe their existence to having winners as ancestors, and everyone today is designed, at least in some circumstances, to compete.

Personalities differ in at least five major ways: whether a person is sociable or retiring (extroversion-introversion), whether a person worries constantly or is calm and self-satisfied (neuroticism-stability), whether the person is courteous and trusting or rude and suspicious (agreeableness-antagonism), whether a person is careful or careless (conscientiousness-undirectedness), and whether a person is daring or conforming (openness-nonopenness). (see The Big Five Model)

Judith Harris has amassed evidence that children everywhere are socialised by their peer group, not by their parents. At all ages children join various play groups, circles, gangs, packs, cliques, and salons, and they jockey for status within them.

Buss designed a questionnaire asking about the importance of eighteen qualities of a mate and gave it to ten thousand people in thirty-seven countries on six continents and five islands—monogamous and polygynous, traditional and liberal, communist and capitalist. Men and women everywhere place the highest value of all on intelligence and on kindness and understanding.

In virtually every country, women place a greater value than men on status, ambition, and industriousness. And in most, they value dependability and stability more than men do.

In every country, men place a higher value on youth and on looks than women do. On average, men want a bride 2.66 years younger; women want a groom 3.42 years older. The results have been replicated many times.

In our society, the best predictor of a man’s wealth is his wife’s looks, and the best predictor of a woman’s looks is her husband’s wealth.

Though the beauty industry is not a conspiracy against women, it is not innocuous either. We calibrate our eye for beauty against the people we see, including our illusory neighbours in the mass media. A daily diet of freakishly beautiful virtual people may recalibrate the scales and make the real ones, including ourselves, look ugly.

The word for “leader” in most foraging societies is “big man,” and in fact the leaders usually are big men. In the United States, taller men are hired more, are promoted more, earn more ($600 per inch in annual salary), and are elected president more: the taller candidate won twenty of the twenty-four elections between 1904 and 1996.

The Meaning of Life

When a rat has access to a lever that sends electrical impulses to an electrode implanted in its medial forebrain bundle, it presses the lever furiously until it drops of exhaustion, forgoing opportunities to eat, drink, and have sex.


Before there were movies, it was adaptive to witness people’s emotional struggles, because the only struggles you could witness were among people you had to psych out every day.

Gossip is a favourite pastime in all human societies because knowledge is power. Knowing who needs a favor and who is in a position to offer one, who is trustworthy and who is a liar, who is available (or soon to become available) and who is under the protection of a jealous spouse or family—all give obvious strategic advantages in the games of life.

Free will is another enigma (see Chapter 1). How can my actions be a choice for which I am responsible if they are completely caused by my genes, my upbringing, and my brain state? Some events are determined, some are random; how can a choice be neither?

Maybe philosophical problems are hard not because they are divine or irreducible or meaningless or workaday science, but because the mind of Homo sapiens lacks the cognitive equipment to solve them. (Cognitive Closure)