Michael's Reviews > Behave: The Biology of Humans at Our Best and Worst

This is an outstanding and monumental synthesis on the causes of behavior by a talented researcher and teacher. He excels in making the science of the brain and behavior accessible to a wide audience without oversimplification. The goal is to provide a handle on how to account for the origins of the most admirable and most despicable of human actions, i.e. the roots of empathy and altruism on the one hand and violence, war, and genocide on the other.

Sapolsky’s accomplishment yields an expansion of what we mean by the biological basis of behavior, enough knowledge of brain systems to make you dangerous, and a better appreciation of the interplay between cognitive and emotional contributions to our actions. You will come away with a better appreciation of human evolution, an informed perspective on whether our hunter-gatherer ancestors were more aligned with a Hobbesian dog-eat-dog character or of an Edenic Rousseau types. In the end, he mounts an assault on the need for a concept of free will, arguing that it is equivalent to putting a homunculus in the driver’s seat above the material universe. His mantra is for a multifactorial and hierarchical array of causes behind behavior. In the end it will be easy to conclude that the extreme complexity of the brain limits the gains in explanatory power from any simplistic reductionist plan. I this vein, I liked the quote from Hilary Bok:

The claim that a person chose her action does not conflict with the claim that some neural processes or state caused it; it simply redescribes it.

Sapolsky’s organizing principle of serving up mountains of research progress according to different timescales that precede particular behaviors is a very helpful approach. Looking at events a second before a behavior taps into automated and unconscious processes in the brain; seconds before brings in higher neural systems associated with conscious actions; hours to days before is the realm of hormonal influences; days to months before the impact of things like chronic stress and adaptations of neuroplasticity; years and decades before includes the shaping of culture and individual development; and centuries to millennia before the processes of evolution. You’ll be busting at the seams by the time you get through this program. He is so skilled at introducing humor and commonsense translations to the concepts presented you will be amazed in your ability to follow his presentation and never fall asleep. If some of the presentation doesn’t quite sink in, he excels in summary take-home messages at the end of each chapter and provision of frequent links among the chapters.


A big plus for me was his overall humility and restraint in claiming more than is reasonably warranted from the data. He is scathing for the excessive claims such as of genetic causes of bad behavior (e.g. calling a variant of a monoamine oxidase gene that provides limited predictability for violent behavior a “warrior gene”), use of premenstrual syndrome as a claim of diminished responsibility in a court defense, and the puffing up of the evidence about “mirror neurons”, which are active both when a primate acts and observes the same act in another, as the foundation of empathy and altruism. The stupendous advances from being able to assess activity of significant brain structures in humans through functional magnetic resonance imaging are also subject to overinterpretation, which I think he mostly avoids. I liked his outrage that the problem of PTSD depended on brain scans showing shrinkage of the hippocampus to get Congress to recognize the problem as worthy of expanding treatment resources. For me, I was more impressed by the power of images of changed receptors in the meth addict’s brain to justify more funding of substance abuse treatment as a “brain” disease. The principle is the same: these people need help in the social and psychological realm, and using images as a reification of their state doesn’t really change the situation. That said, I was disappointed with his simplistic summary that schizophrenia is a “biochemical disorder” and dyslexia a result of “microscopic cortical malformations”.

The interdisciplinary nature of the topics here raises the issue of reliability of the presenter in interpreting the research. I appreciate how the author has a solid track record both in field studies of dominance and aggression in baboons and in laboratory studies on hormonal and brain system roles in social behaviors. Having been a researcher in the area of brain mechanisms of aggression and motivational systems for several years, I can testify to the veracity and wisdom of his analyses of brain studies. As my former scientific career ended up mostly in the area of brain development and plasticity, I can say he was inaccurate on the status of research on a couple of subjects (e.g. the claim of long distance sprouting of new connections to account for repurposing of the visual cortex in blind people; the conclusion that the extensive neuron cell death during development serves primarily an error-correction function).

Can the average reader handle and dig all the brain talk in this book? I think the author does a great job keeping the jargon down in the narrative and slipping a lot of the details into copious footnotes, providing a primer on basic neuroscience in an appendix, and justifying significant points with a huge collection of references stored in the back. A couple of areas of the prefrontal cortex, the amygdala, and the dopamine reinforcement system get the starring role in most of the studies discussed. As an example, here is a bit on the dorsolateral and ventromedial prefrontal cortex:

The dlPFC is the decider of deciders, the most rational, cognitive, utilitarian, unsentimental part of the PFC. …In contrast to the dlPFC, there’s the ventral part of the PFC, particularly the ventromedial PFC (vmPFC). …This is ..an honorary member of the limbic system because of its interconnections with it. Logically, the vmPFC is all about the impact of emotion on decision making. And many of our best and worst behaviors involve interactions of the vmPFC with the limbic system and the dlPFC.
…Consider a classic moral quandary—is it okay to kill one innocent person to save five? When people ponder the question, greater dlPFC activation predicts a greater likelihood of answering yes.…

In this bit on dopamine, I give you a taste of his humor:
Though the dopamine system is similar across numerous species, humans do something utterly novel: we delay gratification for insanely long times. No warthog restricts calories to look good in a bathing suit next summer. No gerbil works hard at school to get good SAT scores to get into a good college to get into a good grad school to get a good job to get into a good nursing home.

Here is a sample on the amygdala, long linked to a major role in fear and anxiety:
Amygdalae are prepared to learn to associate something bad with Them.
So if whites see a black face shown at a subliminal speed, the amygdala activates. But if the face is shown long enough for conscious processing, and anterior cingulate cortex and the “cognitive” dlPFC then activate and inhibit the amygdala.
…This is so depressing—are we hardwired to fear the face of someone from another race, to process their face less as a face, to feel less empathy? No. For starters there’s tremendous individual variation …Moreover, subtle manipulations rapidly change the amygdaloid response to the face of an Other.

Here is a good example of his humility in the face of the brains complexity:
A “neurobiological” or “genetic” or “developmental” explanation for a behavior is just shorthand, an expository convenience for temporarily approaching the whole multifactorial arc from a particular perspective.
Pretty impressive, huh? Actually, maybe not. Maybe I’m just pretentiously saying, “You have to think complexly about complex things.” Wow, what a revelation. And maybe what I’ve been tacitly setting up is this full-of-ourselves straw man of “Oooh, we’re going to think subtly. We won’t get suckered into simplistic answers, not like those chickencrossing-the-road neurochemists and chicken evolutionary biologists and chicken psychoanalysts., all living in their own limited categorical buckets.”

Sapolsky shines in his overview on the roles of testosterone on aggression, of oxytocin on empathy and prosocial behavior, and of stress on both realms of behavior. I liked his conclusion that no drug or hormone or gene can be said to cause a behavior. And all we know of a person’s state of brain health, genetic background, and experience does not provide a reliable predictor of bad or good behavior. At a critical point Sapolsky illustrates the importance of a multifactorial outlook by considering whether a particular woman will suffer from depression. Having a certain variant of the serotonin transporter gene has at most a 10% predictive power. But adding development in poverty, experience of child abuse, levels of glucocorticoids in the bloodstream, living in a collectivist culture, and menstrual status might bring you up get you up to a 50% level of prediction. This illustrates both progress in understanding the causes of behavior and the limitations of such knowledge.

The author hits a popular vein in his chapter on adolescence. The late maturation of the prefrontal cortex and its function to in reigning in excessive emotionality or impulsive behaviors is held to represent a biological foundation for the folly of youth. I’m not sure what benefits we get in how to treat teenagers wisely with this knowledge over the standard psychological consideration of them as being immature. We are not far from McLean’s model of the Triune Brain, with the neocortex in primates an evolutionary wonder that is seen as riding herd on the unruly mammalian limbic system and lizard-brain of the brainstem like Freud’s Superego over the Id. And emphasizing to parents and teachers the risks of teens’ late development of executive brain functions practically puts them in the category of the brain-damaged. Still, it was fun to experience how eloquent Sapolsky gets on the subject:

If by adolescence limbic, autonomic, and endocrine systems are going full blast, while the frontal cortex is still working out the assembly instructions, we’ve just explained why adolescents are so frustrating, great, asinine, impulsive, inspiring, destructive, self-destructive, selfless, selfish, impossible, and world-changing.

Where it comes to egregious acts of violence or crime, neuroscience provides little new ground for or against excusing someone’s responsibility for their acts on the basis of biological causes not in the person’s control. Still, an essential role of the criminal justice system is to “protect the endangered from the dangerous”. And despite any solid way to predict dangerousness, juries need to consider diminished capacities for judgment among the accused. Knowledge about the delayed maturation of frontal cortical systems in adolescents helps to justify being more lenient on them in the justice system. The philosopher Stephen Pinker and neuroscientist Michael Gazzanaga both lean with Sapolsky toward the concept that free will is an illusion, but they still argue we must hold people responsible to varying degrees for violent criminal acts. The argument that a man can’t help being a pedophile but is responsible for acts of child abuse is compelling. But Sapolsky holds his ground that the latter acts are biologically determined no less than the ingrained proclivity to fixate on children and to think otherwise reflects an unscientific dualism of an ethereal homunculus pulling the strings. He doesn’t have a practical answer for reforming the criminal justice system, though he did launch an ongoing discussion between a group of jurists and social scientists and a set of neuroscientists starting with a workshop. One can expect further encroachment of neuroscience into the courtroom, which Sapolsky hopes will proceed with great caution:
Perhaps we’ll have to settle for making sure our homuncular myths are benign and save the heavy lifting of truly thinking rationally for what matters—when we judge others harshly.

Hopefully, the new science of unconscious biases among juries and judges can also be applied to help mitigate some of the excess manipulations of the prosecutors and defense lawyers. For example, research showing that sentences rendered by judges tend to be more severe when they are hungry (i.e. right before lunch). And all members of society (and jury members) must somehow be on guard for subterranean perceptions like the following:

From an early age, in both sexes and across cultures, attractive people are judged to be smarter, kinder, and more honest. We’re more likely to vote for attractive people or hire them, less likely to convict them of crimes, more likely to dole out shorter sentences. Remarkably, the medial orbitofrontal cortex assesses both the beauty of a face and the goodness of a behavior, and its level on one of those tasks predicts the level during the other. The brain does similar things when contemplating beautiful minds, hearts, and cheekbones. And assumes that cheekbones tell something about minds and hearts.

This is a long book, but I wished the author would have spent more time on the nature of war from a biological perspective. I don’t believe he ever broached the subject of territorial aggression, which represents one of the major classes of intraspecies violence found among many species and some primates and the form that most closely resembles human group conflicts that involve killing people over turf. Maybe the outrageous claims of a territorial instinct behind human war by the likes of Desmond Morris and Robert Ardrey nearly 40 years ago still make this a disreputable topic for current scientists to pursue. The discovery that groups of chimps sometimes coordinate together on patrols and raids into another chimp community and kill members they encounter was a shock to many who imbibed Jane Goodall’s portrait of their communities, and obvious analogies to human war were made in the media. Usually territorial conflicts in animals are resolved through symbolic displays that provoke a withdrawal by the intruders of another groups’ territory. The professor I worked with on a brain region that appeared to organize the freeze-flight-fight system in rats in the early 70’s, David Adams, went on to lead efforts that emphasized that the technology and weapons humans use in group conflicts in the historical period makes war a different kettle of fish from animal territorial aggression because the distances over which the weapons operate preclude use of the usual behavioral signals that moderate lethal outcomes. As part of his work for UNESCO he helped facilitate the drafting of the Seville Statement on Violence in 1986, a proclamation signed by 20 prominent scientists that aimed “to dispel the widespread belief that human beings are inevitably disposed to war as a result of innate, biologically determined aggressive traits” (see http://www.culture-of-peace.info/).

A lot of the debate about biological foundations of lethal violence in humans centers around studies of contemporary hunter-gatherer societies and anthropological evidence from ancient human remains. Popular books by people like Jared Diamond and Stephen Pinker interpret such data to indicate that prehistoric humans were always perpetrators of war. Sapolsky spends significant time on the criticisms from various sources on the veracity of the data from hunter-gatherer societies and argues that the advent of agriculture and fixed settlements made warfare more deadly because conflict resolution by moving to a new territory became a less feasible option. The thesis in Pinker’s recent book, “Better Angels of Our Nature”, that the death rate from war has declined substantially over the historical period does not really figure into considerations of the prehistoric hunter-gatherer origins of our species. Nevertheless, Sapolsky criticizes his use of data on death estimates from some historical genocidal events without taking into account their long duration (e.g. centuries for the black slave trade and colonial annihilation of Native Americans). After taking duration as well as population density into account, wars and genocides of the 20th century account for half of the top 10 events of megadeath from violence in known history (surprisingly the Rwandan genocide makes the list under this framework due to its 700K deaths over only 100 days).

Much food for thought can be found in this important book. If you want to learn a bit more about Sapolsky the man and his fascinating field work on baboons, I highly recommend his A Primate’s Memoir: A Neuroscientist's Unconventional Life Among the Baboons . This book was provided by the publisher for review through the Netgalley program.