Some thoughts on ecology, evolution and economics

Behave: Neurobiology in the real world

WIRED magaxine

In his 2017 book, Behave, Robert Sapolsky takes us on a tour of the human brain and illuminates who we are as a species, as a community and as moral beings. He makes it clear that the morality of any behaviour, whether violent or gentle, is mostly a matter of context. Still, we all have the equipment to avoid danger, to seek prestige and to act out of compassion. Our choices in that regard are processed in particular parts of our head and allow neuroscientists to lay bare much of the inner working of our mind. Yet, knowing which parts of our brain are working hardest during a particular decision does not allow scientists to read our minds or predict what we will do. A brain scanner can only map the intensity and trajectory of our thought process. Table 1 outlines some of the parts of the brain that are discussed in the book.

Associated emotions/thoughts
amygdalacenter of brainfear, pain, passion
dl-prefrontal cortexforehead,esp. above eyesocketslogic, doing the hard thing
vm-prefrontal cortexforehead, above the nosesocial connection, being discrete
insulabetween the amygdala & the prefrontal cortexdisgust
accumbenslower part of the skull above the nasal cavitypleasure
anterior cingulate cortexbehind the prefrontal cortexconflicting choices, meaning
Table 1: Parts of the brain featured in Behave (2017) by Robert Sapolsky

Testosterone and violence

There are many reasons to believe that high testosterone levels in our blood stream causes people, mostly men, to be violent. It is well known as a “performance-enhancing” drug, promoting glucose metabolism and a sense of confidence. It also has an effect on the facial recognition circuits in our brain, resulting in greater suspicion of strangers and angry faces. Sapolsky, however, concludes that, when it comes to choosing violence, the brain does not respond to variation in testosterone levels within a normal range.. The greater factor is the person’s history with and disposition to violence. If aggression can improve or maintain someone’s social status, testosterone will make us more inclined to threaten or attack. However, testosterone’s main role is to focus our minds on social status and can lead to greater generosity and honesty in situations where these will clearly lead to a better standing in the community.


The “fight or flight” or stress response is a signal from the brain for the adrenal glands to produce adrenaline. This occurs in all vertebrates and helps ensure survival by allowing bursts of enhanced perception and movement. In a social species , it has the side effect of “chronic stress” where the body and the brain are worn down by extended emergency status. This is especially true in humans, since we can cause adrenaline to be released just by thinking about our fears. Chronic stress tips the balance of decision-making towards the fear-driven amygdala and delays the development of the long-term thinking, logical pre-frontal cortex. Adrenaline’s impacts on the brain are similar to testosterone, making us more aware of angry faces, more egotisitical and, in some instances, more violent. Children exposed to a lot of stress, or childhood adversity, have reduced learning ability, more susceptibility to addiction and a greater vulnerability to depression.

Are behaviours inherited?

Do genes pass on certain behaviours or psychological conditions? It is an obvious question since every behaviour is the result of a set of enzymes and structural proteins in our brains and hormonal glands. The answer is difficult to come by. Using twin studies, we can show how certain behaviours, such as resilience, aggression or leadership potential are more regularly shared between identical twins than between fraternal twins (who share only half the same genes). The tendency, however, is to inflate the genetic effect over the effect of everything else (the environment). One way to do this is to measure the effect of genes in only one environment. Sometimes a gene can produce the same behaviour in many environments but usually the results are less consistent. In one study, violent behaviour could be reliably predicted by a single gene, MAO-A. However the behaviour only expressed itself in people who had experienced severe childhood abuse. Like many physical traits, behaviours are indeed the result of multiple, maybe thousands, of genes. Despite whole genome studies with thousands of individuals we are not closer to predicting human behaviour through a knowledge of our genetic makeup.

Sapolsky’s book is nearly 800 pages long. It is difficult to address even a portion of his entertainingly presented insights in this post. In a future post, I will take up the book’s sections on empathy, politics and criminal justice. None of these topics can be reduced to simple chemistry or neurology through thte use of a brain scanner but we do learn alot about ourselves along the way.