Understanding people is crucial to disciplines and careers ranging from psychology to sales. While there are countless books about how to relate to people—and sometimes how to manipulate them—few try to get to the core of human behavior in the same way that Behave: The Biology of Humans at Our Best and Worst does. Published in 2017, Behave received widely positive reviews for its educational value, as well as the author’s ability to explain complex concepts and his humorous writing style.
As a child, Robert Sapolsky became both fascinated and horrified with the atrocities of the Holocaust and strove to understand the science behind how people could do such terrible things. That fascination grew into a lifelong study of science and people and led directly to this book. What drives people to do what they do? How is it possible that our species can perform incredible acts of compassion and kindness, yet also horrific acts of violence and hatred? Sapolsky, now a professor of biology and neurology at Stanford University, wrote Behave to explore the myriad influences on human behavior and try to answer those questions, as much as they can be answered.
In this guide, we’ve divided Sapolsky’s ideas along classic “nature versus nurture” lines—in other words, how much we’re influenced by our own innate tendencies, compared to how much we’re influenced by our surroundings and how we were raised. Our commentary will provide background information on Sapolsky’s ideas, provide interesting details to deepen your understanding of the subjects, and examine some scientific theories that conflict with Sapolsky’s.
A warning before we start: Sapolsky’s book tells us that human behavior is an immensely complex subject. Any given act is influenced by a person’s genetics, brain structure, culture, upbringing, environment, and whatever stimuli triggered that act. In other words, there’s no one thing you can point to as “causing” an action—rather, there are countless things influencing that action, making it more or less likely to happen. So, if you’re looking for a clear, concise, and satisfying answer to why we do the things we do, you won’t find one here.
We’ll start by examining the “natural” causes of behavior: that is, biology and evolution. First we’ll discuss the structure of the brain and some of its major functions, then we’ll move on to how hormones influence what we do, and finally we’ll look at some behavioral patterns that have been encoded in us through countless generations of evolution.
Note that, while our genetics do have some bearing on our actions, Sapolsky believes the nature part of the nature versus nurture debate has less impact than many people believe.
(Shortform note: Many researchers today—including Sapolsky—no longer recognize a clear divide between our genetics and our environments when it comes to behavior. Rather, as we’ll see in this guide, just about everything is the result of interactions between nature and nurture. In other words, there’s no such thing as a gene that forces us to act a certain way. At most, one could say that genes predispose us to certain behaviors.)
While numerous things influence what we do, the brain is the command center of the body where the final decisions are made. Therefore, the brain’s design and how it works is an ideal place to begin when discussing behavior.
Sapolsky starts by explaining how the brain works in very general terms. He explains that our thought processes operate in three different “levels”:
1. Top level: neocortex. This is the most recently evolved part of the brain and a feature we share only with our closest animal relatives, the primates. The neocortex is associated with deep thought, reasoning, memory, and processing sensory information. Based on what you’re thinking about, the neocortex sends signals down to the limbic system.
2. Middle level: limbic system. The limbic system is found in all types of mammals, meaning that it evolved earlier than the neocortex. The limbic system is associated with emotions; in more scientific terms, with positive and negative responses to stimuli. Based on those stimuli, the limbic system sends signals to the core regulatory functions.
3. Base level: core regulatory functions. This section controls our most basic and instinctive processes—the things you have little or no control over. For example, if the oxygen levels in your blood fall too low, the reptilian complex will signal you to start breathing more heavily, which is why you start panting when you’re exercising.
(Shortform note: Some sources refer to the base level as the “reptilian complex” (which gives rise to the colloquial “lizard brain”). However, Sapolsky doesn’t use that term in Behave.)
Sapolsky adds that, in some cases, thought processes can skip the neocortex and (more rarely) the limbic system, generating much faster and more instinctive responses.
For example, if you read a recipe, you might think it sounds delicious (neocortex), triggering a positive emotional response (limbic system), sparking feelings of hunger and causing you to salivate (reptilian complex). However, if you see or smell food, it would skip the reasoning step and jump right to the emotional response, followed by the physical one. If you’re starving and your blood sugar is low, that signal would skip straight to the base reptilian complex of your brain and make you feel physically hungry—no logic or emotion needed.
Controversy Over the “Three Levels” Model
The brain model that Sapolsky explains here (sometimes called the Triune model) isn’t universally accepted. Some neurologists argue that it shouldn’t be used anymore due to several major shortcomings:
1) The Triune model says that there are three separate and distinct areas of the brain, that each carries out a different function, and that they have little or no interaction with each other. In reality, our various brain functions (rational thought, emotions, and automatic reflexes) are inseparable; each constantly influences the others.
2) The Triune model suggests that, as we evolved, we gained all-new brain features, while the existing features remained mostly unchanged. That is not accurate—the core functions had to evolve and change as the limbic system developed, and both “lower” regions had to evolve to work with the neocortex.
3) Finally, the Triune model imagines the brain as three physically separate regions, when in reality there is significant overlap between the “layers.”
Sapolsky admits these shortcomings of the Triune model in Behave, even saying that the three “levels” should be viewed as metaphorical rather than literal (due to the physical and functional overlaps). However, he still promotes the Triune model as a simplified, easily digestible way to understand the brain and its functions—in other words, he believes it’s still suitable for laypeople, if not for neuroscientists.
The amygdala is part of the limbic system, the “middle” level of the brain, and controls our feelings of fear, anxiety, and aggression.
Sapolsky says that our brains will naturally organize people into two groups: “us” and “others” (sometimes you might hear this as “in-group” and “out-group”). We feel positive emotions (pride, empathy, love, and so on) toward people whom we’ve determined are like us, and negative emotions (hatred, fear—emotions controlled by the amygdala) toward those we’ve decided are “others.”
Notably, the amygdala can activate much more quickly than the neocortex, meaning that our fear and hostility response to an “other” is automatic. The logic-based neocortex will then (hopefully) override that response.
To illustrate the point, Sapolsky shares a study where subjects were shown images of people of different races while hooked to a brain scanner. People’s amygdalas would activate upon seeing such an image for just one-tenth of a second—too short a time for the subjects to even identify what they’d just seen, or to consciously feel their response to it. If the image remained onscreen for longer, the frontal cortex would then kick in and soothe the aggressive response.
Other Functions of the Amygdala
While the amygdala is traditionally associated with fear and the classic “fight or flight” response, recent research suggests its functions may be more complex than simply identifying and responding to threats, including:
Evaluating stimuli. In other words, determining whether they’re positive or negative, and therefore what kind of emotional response is needed.
Memory. The amygdala may be involved in processing and storing memories that have strong emotional components.
Addiction. Some experiments have found that stimulating the amygdala increases subjects’ desire for addictive drugs. One study found that rats would work about three times harder for cocaine when the drug was paired with stimulating the amygdala; conversely, when the amygdala was deactivated, they didn’t want the cocaine at all.
Social interaction. Though the exact reasons aren’t yet understood, researchers have found that amygdala damage can impair our social skills and our ability to empathize with others.
The frontal cortex is the part of the neocortex at the very front of the brain, and it’s involved in reasoning, conscious decision-making, and self-control. As such, Sapolsky says that the frontal cortex is, more than any other part of the brain, what shapes a person’s personality and choices. In other words, the frontal cortex is what makes us who we are.
Sapolsky also says that the frontal cortex is the last part of the brain to finish developing—in fact, it’s not considered fully developed until a person’s mid-20s. Furthermore, the frontal cortex is shaped by experiences much more so than by genes. These facts have profound implications for the “nature versus nurture” debate: Sapolsky argues that a person’s upbringing has a much greater impact on his or her character than genetics do.
(Shortform note: From adolescence to our mid-20s, countless variables impact how the frontal cortex develops. Since, as Sapolsky says, the frontal cortex is crucial to our decision-making processes, that means that everything from the food we eat, to the air quality where we grow up, to how much sleep we get has a significant impact on who we eventually become.)
For all the common talk of nature versus nurture, Sapolsky tells us that nurture can have real and significant impacts on our biology—our nature. For one thing, the brain’s physical structure can change to adapt to various circumstances and stresses. For example, an artist’s brain might have a significantly larger cerebellum than normal (the cerebellum is associated with visualization and fine motor skills). In a sense, your brain behaves like your muscles: The parts you use the most become bigger and stronger.
Furthermore, these physiological changes to the brain can have significant impacts on our behavior. A naturally thoughtful person might develop a stronger neocortex and become even more thoughtful and rational, while an impulsive and emotional person could go in the opposite direction and become even more emotionally driven.
However, the opposite holds true as well: With sustained effort, we can train our brains to strengthen character traits we like and weaken traits we don’t like. As Sapolsky says more than once, environment and experience have greater impacts on our behavior than biology.
Two Types of Neuroplasticity
While Sapolsky mostly discusses how everyday events reshape our brains, neuroplasticity also gives us a remarkable ability to recover brain function after disease and injury. Researchers recognize two different forms of neuroplasticity:
Structural Plasticity. The brain’s structure changes in response to which parts of it get used the most—this is what Sapolsky discusses at length in Behave.
Functional Plasticity. The brain adapts to disease or injury, enabling healthy parts of the brain to take on the functions of damaged portions.
The brain accomplishes both of these feats by strengthening the neurons (nerve cells) that we use the most, while the connections we don’t use deteriorate—those neurons may even die and get reabsorbed by the body in a process called synaptic pruning.
While the brain ultimately decides what we’ll do, making those decisions requires input from the entire body. A great deal of that input relies on, or is influenced by, hormones—chemicals that initiate and regulate various functions.
There are dozens of hormones at work within the human body, but Sapolsky focuses on the ones that are especially relevant to behavior—specifically, dopamine, serotonin, oxytocin, and testosterone.
Dopamine is a neurotransmitter that promotes goal-oriented actions; think of it as the “motivation hormone.” Interestingly, Sapolsky says that dopamine is more about the anticipation of a reward than about enjoying the reward itself—in other words, we get dopamine boosts when we work toward a goal, not just when we achieve it.
Serotonin is another neurotransmitter associated with happiness and motivation. Sapolsky says that serotonin works in conjunction with dopamine to enhance its effects, particularly when it comes to long-term goals. Low serotonin is linked with impulsiveness, aggression, and antisocial behavior—though, strangely, high serotonin levels have been found to have the same effects. As with everything about human behavior, Sapolsky says that serotonin’s exact effects depend on numerous other variables, and even the scientists running the studies can’t always say what those variables are.
(Shortform note: Deficiencies in dopamine and serotonin are believed to cause various mental health disorders. For example, some researchers believe that a lack of dopamine causes—or at least contributes to—Attention Deficit Hyperactivity Disorder (ADHD). The dopamine deficiency causes people with ADHD to quickly lose focus on goals, and they have difficulty with emotional regulation. Similarly, many doctors believe that a serotonin deficiency contributes to depression.)
Oxytocin (and the closely related hormone vasopressin) reduces aggression, increases empathy and trust, and promotes bonding behaviors like physical touch or eye contact. In short, oxytocin and vasopressin cause us to act in a more prosocial way—that is, in ways that are supportive and helpful to others. Furthermore, experiencing prosocial behavior causes us to produce more oxytocin, creating a positive feedback loop.
However, Sapolsky warns that the apparently-positive effects of these hormones greatly depend on context: While oxytocin and vasopressin make us more helpful to people in our in-group, they actually make us more aggressive and suspicious toward those who aren’t. In other words, they strengthen the bonds we already have, but also make us more insular and hostile toward outsiders.
(Shortform note: In addition to making us more aggressive toward “outsiders,” oxytocin can also make us more forgetful. However, oxytocin’s effects on memory—like so many things Sapolsky discusses—seem to be context-dependent. Briefly, the researchers found that people who are more comfortable relying on others scored worse on a memory test after taking oxytocin, while more independent people actually scored better after taking it. The researchers concluded that more study was needed to determine exactly how oxytocin affects memory, and how it interacts with people’s tendencies toward independence.)
Testosterone increases self-assurance and optimism while decreasing anxiety. It also suppresses part of the neocortex while boosting limbic system activity—in short, it makes you more impulsive and less rational.
Sapolsky says that many people think testosterone causes aggression. However, while there is a correlation between testosterone and aggression, it’s not as strong nor as direct as previously thought. In fact, if anything, it appears to be the other way around: Aggressive behavior leads to testosterone production, rather than high testosterone levels leading to aggressive behavior.
(Shortform note: As people age—especially men—reduced testosterone levels can cause physical and emotional changes. Most notably, people may experience decreased bone and muscle strength, as well as a loss of motivation and a generally depressed mood. Doctors have found that testosterone therapy can reverse some of these effects in aging men. Some men have reported feeling younger and stronger after taking testosterone supplements, but there’s little scientific evidence supporting it as a treatment for those with normal testosterone levels for their age.)
Our brains and hormones—and all of the “natural” effects on our behaviors—work the way they do because of evolution: Ancestors who behaved in certain ways were more likely to survive and reproduce, passing on the genes that caused them to behave in those ways. So now, many generations later, those genes still survive in us and influence our behavior.
Let’s examine a few broad categories of human behavior closely related to survival and reproduction.
(Shortform note: In The Selfish Gene, Richard Dawkins makes the case that human behaviors are becoming less genetically driven as we continue to evolve. In particular, he believes that our advanced brains—our consciousness—give us the ability to go against our genetically programmed instructions. For example, our genes should compel us to have as many children as we can feasibly raise, but many people choose not to reproduce at all. However, even Dawkins doesn’t think we’ll ever be totally free of genetic imperatives; if nothing else, we’ll always be driven to keep ourselves alive.)
Kin selection is a term in evolutionary biology that means potentially sacrificing your own welfare or reproductive success in favor of your relatives’—for example, risking your life by fighting off a home intruder to protect your family. It evolved because, by definition, your relatives share many of your genes, so keeping them alive helps pass those genes on.
Sapolsky says that kin selection explains a great number of human behaviors, but that we can also find countless examples of people going against what kin selection should dictate. For instance, we can read news articles about people killing family members, or millionaires donating incredible amounts of money to strangers.
Sapolsky’s theory is that humans do follow kin selection, but the way we decide who our “kin” are isn’t entirely rational. On the one hand, we can look at total strangers and find similarities to ourselves. On the other hand, we can reject even our closest family members if they, for instance, behave in ways we find unacceptable.
Furthermore, we can be manipulated into feeling more or less related to others. Propaganda can paint groups of people as dangerous and monstrous—barely even human, let alone kin. And, conversely, campaigns emphasizing people’s humanity and similarities to us have been crucial in everything from promoting LGBTQ+ rights to raising funds for cancer research.
Hamilton’s Rule of Kin Selection
Hamilton’s rule quickly and efficiently explains kin selection. Hamilton’s rule is the equation r * B > C, (r times B is greater than C), where r is relatedness, B is the benefit to the recipient, and C is the cost to the one taking action.
For example, your sibling has 50% of the same genes as you do (on average), so your r is 0.5. Therefore, if an action would have more than twice as much benefit to your sibling as cost to you, kin selection dictates that you would perform that action. A half-sibling would have an r of 0.25, so the benefits would have to be more than four times greater than the cost to you.
While this equation only directly applies to people who are genetically related to you, it can provide a hint about how far you’d be willing to go for someone. How close do you feel to this other person? For example, do you think of him like a brother, or is your relationship more like close cousins? How you answer those questions could change the r value of Hamilton’s rule, even when it should logically be zero.
A related phenomenon (no pun intended) is reciprocal altruism—the theory that it’s often advantageous for unrelated individuals to work together. To give a common example, grooming behavior is common among animals that live in groups—any member of the group will groom any other member, because making sure nobody’s carrying fleas or ticks benefits the whole group.
Sapolsky says that human society was founded on reciprocal altruism. Hunter-gatherer societies, the earliest known type of human civilization, relied heavily on nonrelatives working together to keep everyone safe and fed. Therefore, reciprocal altruism is in our genes at least as strongly as kin selection is.
Reciprocal Altruism and the Tit for Tat Strategy
In The Selfish Gene, evolutionary biologist Richard Dawkins uses the Prisoner’s Dilemma to illustrate how reciprocal altruism could have evolved. In the Prisoner’s Dilemma, two players have the choice to “cooperate” or “betray,” and each must choose without knowing what the other player picked. The possible results are:
Both cooperate—both players gain a small number of points.
One cooperates, the other betrays—the cooperating player loses a large number of points, the betrayer gains a large number of points.
Both betray—both players lose a small number of points.
Professor Robert Axelrod hosted a Prisoner’s Dilemma tournament, where he asked people to design computer algorithms that would play hundreds of rounds of Prisoner’s Dilemma against each other. The winner was a simple program called Tit for Tat, which would always start out cooperative, then for each subsequent round it would copy what its opponent did the round before. It was mathematically impossible for Tit for Tat to win any individual match, but over the course of the tournament it racked up more total points than any other program.
Dawkins argues that the Tit for Tat program demonstrates why reciprocal altruism works better than more aggressive strategies: Aggressive individuals think of life as a zero-sum game—one where there must be a winner and a loser—and therefore they worry about defeating their opponents rather than simply doing well for themselves. However, in Prisoner’s Dilemma (and in life), all players can do well for themselves by cooperating and not worrying about “winning.”
Finally, empathy (echoing another person’s feelings) and compassion (acting to improve another person’s situation) have their place in our behaviors.
On the surface, empathy and compassion don’t seem to follow the same kind of evolutionary logic as kin selection or reciprocal altruism—we don’t seem to benefit from sharing another’s pain, or from acting to alleviate it. However, Sapolsky says that compassionate acts can (and usually do) have selfish aspects to them: A boost to our reputation, a sense of pride in our actions, or just the pleasant rush of dopamine that comes from doing a good deed.
It’s still not totally clear how empathy and compassion evolved, but it seems obvious that helping others is somehow advantageous. One theory Sapolsky favors is that empathy and compassion go hand-in-hand with our evolving brains and cultures: As we get better at reasoning and rational thought, we realize more and more that helping strangers benefits all of us.
(Shortform note: As a partial counterpoint to Sapolsky, many animals show signs of empathy and compassion toward one another. It’s likely that our evolving brains made us better able to rationalize those feelings, and perhaps to foster them where they wouldn’t otherwise exist, but it’s misleading to say that only species with highly developed brains display empathy.)
While biology explains internal influences on human behavior, Sapolsky says that external influences—including how we’re raised, where we are at a given moment, and what’s happening around us—are even more important in determining how we act.
Humans, like many other animals, instinctively want to fit in. We want to be part of the in-group, so we obey our culture’s rules, follow its beliefs, and expect others to do the same. Realizing that we’re not matching the people around us can cause serious anxiety—just imagine showing up to a fancy party in jeans and a t-shirt.
Interestingly, studies show that our most deeply held values aren’t things that we consciously think about following. For example, someone who’s been raised to be honest doesn’t decide to tell the truth or overcome the temptation to lie; that temptation never arises in the first place. In other words, you’ll reflexively follow whatever core values you were raised with, unless you make an active effort to do otherwise.
Two Types of Culture
In The Culture Map, cross-cultural management expert Erin Meyer discusses two different styles of culture, which she calls “peach cultures” and “coconut cultures.”
Peach cultures are outwardly friendly, but keep what’s important to them deep inside and only share it with a select few people—like how a peach has soft flesh with a hard inner pit. The US is an example of a peach culture.
Coconut cultures are the opposite: Outwardly cold and distant, but much more willing to share their true selves once you break through that shell. Russia is an example of a coconut culture.
These differences come down to different core values. Someone raised in a peach culture will reflexively treat people politely, yet find it very difficult to open up to others. Someone raised in a coconut culture will find it difficult to be warm and welcoming to strangers.
Throughout history, one of the most influential parts of a person’s upbringing has been his or her religion. Sapolsky says that all religions share a few traits in common, which makes them ideal for understanding cultural effects on behavior:
Three Levels of Belief
Beliefs such as religion influence our behaviors in various ways, based largely on how strongly we hold those beliefs and how emotionally invested we are in them. In Awaken the Giant Within, Tony Robbins breaks down beliefs into three categories:
1. Opinions: the weakest kind of belief, with little emotional investment. For example, preferring tea to coffee is an opinion—someone might state that preference but wouldn’t feel the need to defend it and might even find that opinion changing over time.
2. Beliefs: much stronger than opinions and based on personal experiences or information from trusted sources. People generally aren’t willing to listen to anything that contradicts a belief; they’ll ignore or deny any such information. However, close friends or trusted authorities on that subject may be able to change those people’s minds over time.
3. Convictions: the strongest type of belief and central to our understanding of the world, and we shield them with intense emotions. We’re likely to become angry and combative if anyone—even a close friend—so much as questions one of our convictions.
So far, we’ve discussed how biology and neurology shape our behavior through nature and how culture affects our behavior through nurture. Now we’ll examine the most direct influences on our behaviors: our immediate surroundings and our mental states when we take action.
Sapolsky says people will instinctively act in ways that match their physical surroundings. For instance, people are more likely to commit crimes when evidence of other crimes is present—they might drop their trash on the ground if there are signs of vandalism nearby. In more general terms, people are more likely to violate social and ethical norms if it seems like others have already done so. However, Sapolsky says that the reverse is also true: People are more likely to behave themselves and follow the rules if the environment is clean and orderly.
Our physical environments can also affect us biologically. For example, if you see a dangerous animal, your body will activate genes that cause you to produce adrenaline, so you’ll be ready to fight or run away. Conversely, locking eyes with a child or a pet causes you to produce extra oxytocin, producing feelings of love and kinship.
(Shortform note: Sapolsky mainly discusses the immediate effects of what we can observe around us, but our physical environment affects us in many other, longer-term ways too. For example, certain types of air pollution can cause changes in behavior, mood, and overall health, with effects ranging from irritability to allergies and asthma. Similarly, exposure to heavy metals such as lead can cause increased aggression, fatigue, and memory loss.)
How close we are to a situation—physically and emotionally—greatly affects how we respond to it. For instance, we might jump into action if we see a child in danger but not feel compelled to act if we read a story about child abuse. Similarly, if we know the child who’s in danger, we’re much more likely to do something about it.
How directly we act upon a situation also changes how we approach it. Notably, people generally consider allowing a bad thing to happen to be much more acceptable than doing a bad thing personally; in Sapolsky’s terms, omission (failing to prevent an act) isn’t as bad as commission (committing the act). For example, I might allow someone else to vandalize a disliked neighbor’s house, even if I would never vandalize it myself.
Finally, as with many things, we aren’t totally rational in our moralizing. People who would never steal physical copies of music albums or video games will happily (and illegally) download them from the internet. The reduced risk of getting caught may explain that to some extent, but there’s also the fact that clicking a download link doesn’t really feel like stealing, and thus pirating feels more acceptable than tucking a CD into your jacket does. There’s also a greater sense of distance—both physical and emotional—between you and the victim: Rather than stealing from a shopkeeper whom you can see and talk to, you’re stealing from an artist who might be on the other side of the world.
Developing Morality
Obviously, people don’t all share the same morals—even people raised in the same cultures can have wildly different ideas of what’s right and wrong, based on their own experiences and predispositions.
To help understand how a person develops a personal moral code, psychologist Lawrence Kohlberg breaks moral development into three stages, with each stage helping to shape the ones that come after it:
1. Pre-conventional: the earliest and least-developed stage of morality, where the person’s ideas of right and wrong are based on obeying authority figures and avoiding punishment. In other words, the person doesn’t yet have what we’d recognize as a moral code, just a set of rules to follow.
2. Conventional: the stage of morality when the person simply accepts what society says is right and wrong. This differs from the previous stage because the person is now doing what he or she believes is right, rather than just seeking praise and avoiding punishment. In other words, the person does have a moral code, it’s just a reflection of the moral codes of others.
3. Post-conventional: the final stage of moral development, when the person begins developing his or her own moral code. That code will be heavily influenced by the previous two stages, but at this point the person recognizes that people have different ideas of what’s right and what’s wrong. For example, one person might believe that stealing is always wrong, while another might believe that stealing to feed your family is the right thing to do.
Just like our physical environment and moral codes can influence how we behave, so too can the people who are around us. For a clear and easy example, imagine how you act around your best friend compared to how you act around your boss—in most cases, your behavior will be wildly different.
We’ve already discussed the human tendency to divide people into in-groups and out-groups, but we also subdivide our in-groups into ranks—in Sapolsky’s words, we have hierarchies. We tend to feel closer to those who are close in rank to us in those hierarchies. For example, an office worker would likely feel more kinship with his coworkers than with either the company CEO or the janitor.
A hierarchy is different from typical “us versus them” dynamics because all members are still part of the same group, and (at least in theory) all work together for the common good.
Furthermore, Sapolsky points out that the effects of our social environments go beyond influences from people we personally know. For instance, men tend to become more aggressive and take greater risks when women are present. Also, in situations where helping someone would be inconvenient (but not dangerous), the more people there are present, the less likely anyone is to step forward to help—the so-called “Bystander Effect.”
In situations where helping would be dangerous, however, people are actually more likely to step in if there are witnesses nearby. That might be because of the chance to be recognized as a hero, or perhaps simply because it seems more likely that we’ll have backup if things get out of hand.
Friendship Is a Special Type of Social Environment
The people around us at any given time may affect our behavior in that moment, but the people we spend a great deal of time around can have much more profound and longer-lasting impacts. Behaviors and habits tend to spread throughout friend groups, including eating habits, how often we exercise, whether we smoke, and how much alcohol we drink.
Furthermore, studies have shown that spending time with friends leads to increased happiness and overall higher quality of life. Interestingly, the effects are based less on how many friends we have and more on how close those friendships are. In other words, it’s better to have a few good friends than dozens of acquaintances.
Stress increases amygdala function while suppressing the frontal cortex—in other words, it makes us more prone to reflexive, habitual, and selfish behavior, and less able to regulate that behavior with logic and reason.
Furthermore, Sapolsky says that one of the most effective ways to reduce stress is to behave aggressively toward someone else. For example, someone who’s stressed out at work is more likely to lash out verbally or physically at “safe” targets like a spouse or a child, because that helps relieve the stress. Note that Sapolsky does not excuse this behavior; he’s merely offering a partial explanation of the neurology behind it.
The Effects of Chronic Stress
While short-term stress can make us unpleasant (or even dangerous) to be around, long-term stress is known to have devastating effects on the body and mind. Mayo Clinic says that chronic stress—and long-term exposure to stress-related hormones such as cortisol—can lead to numerous health problems, including:
Anxiety and depression
Heart disease
Insomnia
Memory loss
Furthermore, unhealthy stress management techniques like drinking alcohol and overeating only compound these problems. Instead, Mayo Clinic recommends learning some healthy coping mechanisms like working out, or indulging in a hobby.
In When the Body Says No, physician and psychologist Gabor Maté also discusses some of the diseases that chronic stress can give rise to, including multiple sclerosis, irritable bowel syndrome, arthritis, and even cancer. According to Maté, many of these diseases appear more frequently and more severely in people who suffered childhood trauma and neglect, and he argues that they must be cured with a holistic treatment regimen that encompasses physical, mental, and emotional health.
This guide has covered numerous factors that influence our behaviors, but at the end of the day, can we still make a conscious choice about what to do? Sapolsky doesn’t think so—he believes that free will is an artificial construct we use to fill the gaps in our understanding of human behavior. If this is right, then, logically, someday we’ll close up all of those gaps and have no more need (or space) for the idea of free will.
While giving up the concept of free will is a disturbing notion, Sapolsky has some thoughts about why doing so would only change things for the better:
Dangerous people will still be arrested and—if needed—punished. Just because it’s not their “fault” doesn’t mean that dangerous people would be allowed to walk around freely. What it does mean is that justice would no longer focus on punishment, except as a means to discourage them from relapsing into their bad behavior. Instead, the focus would be on fixing whatever caused them to act that way in the first place.
(Shortform note: Studies have shown that rehabilitation is more effective—and cheaper—than punishment-focused prison systems. When prisoners receive health care and mental health treatment, learn marketable skills, and have the opportunity for an education, violence rates in prison drop significantly and prisoners are far less likely to reoffend after release.)
People would still take credit for their good deeds. While it doesn’t make logical sense for people to feel pride in their actions if they didn’t “choose” those actions, it’s unlikely that we’ll ever completely separate ourselves from our egos. Sapolsky’s hope is that we’ll eventually use our concept of free will for harmless things—for instance, taking pride in your skill at a game, or your taste in clothing—instead of using it as a reason to judge and punish others.
Selflessness in Religion and Science
While Sapolsky says that people will probably never separate themselves from their egos, many religions throughout history have urged us to do just that:
Christianity teaches that self-centered thoughts like pride and greed are among the worst sins a person can commit, while selfless acts—charity, diligence, and humility—are among the greatest virtues a person can have.
Hinduism teaches that all things come from God, are part of God, and will return to God (rather than from ourselves).
Buddhism says that we have no “self” as most people think of it. Rather, each of us is one tiny part of a single, universal whole. Buddhism also teaches that all suffering comes from thinking of ourselves as separate from what’s around us.
If we truly have no free will—if we’re nothing but the culmination of our biology and our experiences—then science agrees with religion that we should let go of pride, selfishness, and egotism.
Consider the ways “nurture” influences your behavior.
Recall something you did within the last week: one act that you remember clearly. This might be something you’re especially proud of, or, conversely, something that seemed out of character for you. Describe the action you’ve chosen.
What cultural influences might have led you to that behavior? (Consider the common behaviors and beliefs of your in-group or religion.)
What personal influences might have led you to that behavior? (Consider your experiences, morals, and state of mind at the time.)
Finally, what environmental influences might have led you to that behavior? (Your physical environment, the people who were around you (if any), and how emotionally involved you were in the situation.)