Robert Sapolsky’s Behave

When I saw, earlier this month, that a new book by Robert Sapolsky had hit the shelves, I immediately ran off to purchase it, mentally reorganizing the month’s reading to accommodate this 800-page behemoth. Such is my admiration for Sapolsky, a Stanford professor of neurobiology and one of the world’s foremost primatologists – and in that I am not alone, for his class lectures have drawn well over a million views on YouTube. Think on that: most professors have enough trouble getting their own students to attend their lectures, and yet here is Robert Sapolsky – humble, self-effacing, soft-spoken – drawing an audience of more than a million to hear him discuss the finer points of genes, neurons and hormones, and their role in shaping human behaviour. No doubt some savvy publisher, seeing the popularity of his course lectures, urged him to undertake a book more ambitious than his previous essay collections, something that would synthesize all that he knew – and all that we have learned – about the biological underpinnings of human behaviour, and the result is Behave, a book destined to challenge, provoke and inspire readers for generations.

Sapolsky’s stated aim is to explain human behaviour – the good, the bad and the ugly – and to do this, in his view, demands casting a wide net.

A behavior has just occurred. Why did it happen? Your first category of explanation is going to be a neurobiological one. What went on in that person’s brain a second before the behavior happened? Now pull out to a slightly larger field of vision, your next category of explanation, a little earlier in time. What sight, sound, or smell in the previous seconds to minutes triggered the nervous system to produce that behavior? On to the next explanatory category. What hormones acted hours to days earlier to change how responsive that individual was to the sensory stimuli that trigger the nervous system to produce that behavior? And by now you’ve increased your field of vision to be thinking about neurobiology and the sensory world of our environment and short-term endocrinology in trying to explain what happened.

He has set no small task for himself, but his background gives him unique insights. For over 30 years, for example, he spent his summers in Africa, studying a single troop of baboons, observing them in their best and worst behaviours and, occasionally, darting them with tranquilizer to take blood samples and test their hormonal profiles. Prior to his first trip to Africa, he studied “biological anthropology” at Harvard, taking classes from the famous Edward O. Wilson, the man who is justly considered the father of the field, and whose monumental (and hugely controversial) Sociobiology (1975) argued for a “new synthesis” of sociology and biology. That synthesis has yet to occur, insofar as sociology departments have been stubbornly resisting the encroachment of the biological sciences, but Behave is yet another stunning example of what might be achieved when biological insights are allowed to inform our understanding of human society. Sapolsky is aware of this controversy, but aside from the occasional reference to “a certain breed of social scientist who finds biology to be irrelevant and a bit ideologically suspect,” he seems content to ignore the wider debate and merely present his case. This, I think, is largely to his credit.

One of the central contentions of the book is that it is impossible to understand any given human behaviour in isolation. To ask, for example, what is going on in a person’s brain seconds prior to the commission of a murder or the consumption of a sugary snack necessitates also asking questions about what was going on in their brain earlier that day; and doing so will involve asking about that person’s hormone profile; and asking about their hormones will, of necessity, raise questions about the environmental factors that may have given rise to those specific hormones; and all of this presupposes the existence of biological mechanisms that took hundreds of thousands of years to evolve. In other words, as Sapolsky is fond of repeating, this is deeply complicated stuff. In deference to that fact, three appendices, referred to throughout the book, offer an important refresher on the basics of neurology, endocrinology and the role of proteins, and unless you have a strong background in biology, these are must-reads to make sense of his main arguments.

For the sake of brevity, I will discuss two of the most important brain regions Sapolsky covers, and how their functioning impacts human behaviour. The first region he covers is the amygdala, a part of the limbic system that produces our fight, flight or fear responses, and often does so before our conscious mind can even process what we have seen. If you’re biking in the woods, for example, and you see a snake – or something that even looks like a snake – your amygdala will respond before your brain can process the information and tell you, “Yes, that’s a snake, but it’s a harmless garden snake” or “No, that’s just a snake-like stick.” Or, say you’re attending a horror movie: at the moment that the ax-wielding psychopath is about to strike, the amygdala is responsible for producing that sense of terror in you that causes you to clench your fists or jump out of your seat. It’s also the brain region most directly responsible for producing aggression: you are apt to fight what you cannot flee from. And when you manage to calm yourself down, to remind yourself that you’re in a movie theatre and not actually in harm’s way, you are using your prefrontal cortex, the foremost section of the brain, which happens to also have been the most recently evolved. It is the PFC that provides the contextualizing signals that help calm down the amygdala and mitigate your threat response. The PFC is also involved in contextualizing present actions in the context of a longer future; in Sapolsky’s words, “the frontal cortex makes you do the harder thing when it’s the right thing to do.” And there’s one final bit of fascinating insight about the PFC: it is the brain region that takes the longest to fully develop, and therefore also the region of the brain most susceptible to environmental influence. In men, for example, the PFC is not fully developed until we reach our mid-twenties!

Two experiments, done on these separate regions, should illustrate the vital roles they play in shaping our behaviour. In one experiment, subjects were hooked up to a brain scanner while images were flashed before their eyes for one-tenth of a second – too rapidly to be processed by the conscious mind. When subjects were shown photos of members of their own ethnicity, their amygdalas – I remind you, the regions of their brains processing fear, flight or fight – showed no activity. However, when they were shown images of people who were not of their ethnicity, there was significant amygdala activation. This is a deeply depressing finding, for many reasons, but the case Sapolsky uses to illustrate the catastrophic consequences of this particular study should be painfully familiar to us: an officer, with a suspect in his sights, witnesses the man reach for something in his pocket, forcing him to make a split-second decision: shoot or hold his fire. If the suspect in question is of a different race, there is a good chance the officer’s amygdala is sending signals of panic through his mind, biasing him towards pulling that trigger.

Another study, conducted on children, focused on the prefrontal cortex and the concept of delayed gratification. A scientist offers a child a cookie to eat, but with the proviso that, if the child refrains from eating the cookie while the scientist leaves the room for 15 minutes, the child can have five cookies upon his return. So eat one cookie, or wait a mere 15 minutes and eat six. How many of the children are capable of delaying gratification, and what can be discovered about them based on their decisions? The most striking finding was that there was a large socioeconomic gap associated with choosing to delay gratification: the children of the poor were much less capable of waiting the 15 minutes than were the children of the middle and upper classes. Why might this be? Economic stability, Sapolsky posits, acts as a kind of reassurance that there is a brighter future to be had; poverty, on the other hand, makes immediate gratification more tempting, for who knows what the future will bring? The prefrontal cortex also plays a role in crime prevention: it’s the part of your brain that makes you reconsider your most violent impulses, or think better of chasing down the driver of the car who just cut you off.

These arguments culminate in a final chapter that calls into question both our understanding of free will and the criminal justice system built on that understanding. If human behaviour can be thought of in purely mechanistic terms, as the result of cognitive forces – if, in fact, there is no “soul” or homunculus or coherent “I” at all – then what, exactly, are criminal sentences punishing? A damaged prefrontal cortex? A hormone imbalance? These are, admittedly, uncomfortable questions to raise, and Sapolsky would be the first to admit that neuroscience has not reached an adequate level of sophistication to explain, for example, why one person with an inhibited frontal cortex and a painful family background goes on to commit a murder, while another with the same symptoms lives a successful and law-abiding life, but the greater quarry is free will itself, the very foundation of our concept of justice for thousands of years, and science may have already dealt it a fatal blow.

Behave is a challenging book dealing with a complex subject, but Sapolsky is an expert guide, both erudite and funny, equally at home citing Locke, Rousseau and a host of other philosophers and writers, both ancient and modern, as he is marshalling the latest scientific studies to make his case. If I have one major criticism, it is that I do not believe he has applied an equally rigorous standard to the sociology studies he invokes: two such studies I know to have had serious replicability issues, but he seems unaware of this, even though, for every scientific study he presents, he demonstrates an intimate familiarity with their findings, methodological weaknesses, and relevant criticisms. But this is quibbling on my part, and doesn’t detract in the slightest from what amounts to a guided tour of the human mind, offered by one the world’s foremost experts.