Behave: The Biology of Humans at Our Best and Worst

by Robert M. Sapolsky

  * We even have that profound renunciation of arachnophobia, namely kids becoming bereft when Charlotte dies in Charlotte’s Web.

  * As an important point, throughout this book, whenever I describe work done by Jane Doe or Joe Smith, I actually mean “work done by Doe and a team of her postdocs, technicians, grad students, and collaborators spread far and wide over the years.” I’ll be referring solely to Doe or Smith for brevity, not to imply that they did all the work on their own—science is utterly a team process. In addition, as long as we’re at it, another point: At endless junctures throughout the book, I’ll be reporting the results of a study, along the lines of, “And when you do whatever to this or that brain region/neurotransmitter/hormone/gene/etc., X happens.” What I mean is that on the average X happens, and at a statistically reliable rate. There is always lots of variability, including individuals in whom nothing happens or even the opposite of X occurs.

  * This is termed “Pavlovian conditioning” in a nod to Ivan Pavlov; it’s the same process by which Pavlov’s dogs learned to associate the conditioned stimulus of a bell with the unconditioned stimulus of food, so that the former eventually was able to provoke salivation. Less reliable are “operant conditioning” approaches, in which the degree to which something is scary is assessed by how much an individual will work to avoid being exposed to it.

  * As usual in science, things aren’t all that clean—some of those “plastic” changes during fear conditioning also occur in the central amygdala.

  * Just to make things more complicated, the BLA neurons are probably talking to the central amygdala neurons via middlemen called intercalated cells.

  * I would be remiss not to touch on one issue in this field—when a new fear is learned, where is that memory stored? Next to the amygdala is the hippocampus, which plays a key role in “explicit” learning about straightforward facts (e.g., someone’s name). While the hippocampus is where short-term knowledge about the name is turned into long-term memory, the memory trace itself is most likely in the cortex. The hippocampus, to use a metaphor that will probably be obsolete by the time this book sees the light of day, is the keyboard, the conduit, the portal to the cortical hard drive where a memory is stored. Is the amygdala solely the keyboard (with fear memories stored elsewhere), or is it the hard drive as well? This has been an ongoing, unresolved debate in the field, with the “keyboard + hard drive” view championed by LeDoux and the keyboard-alone view espoused by the equally accomplished scientist James McGaugh of the University of California at Irvine.

  * An example of the sort of complexity we’re up against here: Both fear conditioning and fear extinction involve activation of inhibitory neurons. Hmm, that commonality seems weird, given opposite outcomes. It turns out that extinction involves activation of neurons that inhibit excitatory neurons, while fear conditioning involves activation of inhibitory neurons that inhibit other inhibitory neurons that project onto excitatory neurons. A double negative, equaling a positive.

  * How might you distinguish between sexual motivation and performance in a male rat? Well, the latter is easy—what’s the guy’s frequency and latency when with a sexually receptive female? But sexual motivation? This is measured by determining how often a male will press a lever in order to get access to a female.

  * I can’t resist mentioning a case report of a woman with epileptic seizures initiating in the amygdala. Before seizure onset, she would have the delusion that she was male, including a sense that she had a deep voice and hairy arms.

  * In contrast to this picture of growing, precarious arousal, the amygdala deactivates in both men and women during orgasm.

  * This shortcut has been most cleanly demonstrated for auditory information, by LeDoux. The evidence for other sensory modalities has been more inferential.

  * Just to bring some specificity into it, the precise pattern of which subregions of the hypothalamus and which autonomic relay nuclei are activated can vary with the type of stimulus—thus the fear and aggression associated with responding to a predator are somewhat different from those in response to the menace of a member of one’s own species; similarly, the pattern of response in a rodent to the smell of a cat is a bit different from the response to a cat itself.

  * Apologies to Micah 4:4.

  * Strongly suggesting that these neurons independently evolved on three separate occasions, given the evolutionary distances between primates, cetaceans, and elephants. The nearest relatives of elephants, for example, are hyraxes and manatees. The convergent evolution of von Economo neurons from three separate lineages emphasizes that these cells go hand in hand with major sociality.

  * To give a sense of this, consider someone deciding whether to press a button. The frontal cortex makes its decision; know its neurons’ firing patterns, and you can predict the decision with 80 percent accuracy about seven hundred milliseconds before the person is consciously aware of their decision.

  * This quaintly obsolete paragraph is written with the recognition that most of this is irrelevant in the age of smartphones and the constant companionship of Siri.

  * This test is reminiscent of something called the California Verbal Learning Test (CVLT). My wife, who spent her professional youth as a neuropsychologist, would practice tests on me when she was in grad school; the CVLT was, without question, the worst. It was insanely stressful—I’d be a sopping mess by the time she’d finally call it an evening. But on the other hand, this will pay off handsomely in a few decades when I ace the neuropsych tests out of habit, despite being seriously demented . . . and thus don’t get appropriate medical care. Hmm, I may need to rethink this.

  * There’s a key exception to this, to be covered in chapter 13 on morality.

  * There is an ongoing controversy in this field as to whether it is “willpower” or “motivation” being decreased by cognitive load. For our purposes, let’s think of them as synonymous.

  * The apathy is in contrast to early-stage Alzheimer’s sufferers, who, after making some horrible social blunder due to memory problems—say, asking after the health of someone’s spouse because they didn’t remember that the person died years ago—are mortified.

  * Ian McEwan’s novel Saturday pivots around behavioral disinhibition due to Huntington’s in a central character. It’s brilliant.

  * A quick primer for directions in the brain, for anyone who cares. They come in three dimensions: (1) Dorsal/ventral. Dorsal = the top of the brain (in the same way that the fin on the top of a horizontal dolphin is the dorsal fin). Ventral = the bottom. (2) Medial/lateral. Medial = at the midline of the brain, when viewed in cross section. Lateral = as far as possible from the midline, moving left or right. Thus the “dorsolateral” PFC is the part of the PFC that is on top and to the outside. (3) Anterior/posterior. At the front or back of the brain. Lateralized brain structures come in pairs—one in the left hemisphere, one in the right, both at the same place in the dorsal/ventral and anterior/posterior planes, but in opposite locations in the medial/lateral plane.

  * To help keep “dlPFC” and “vmPFC” straight, I’ll constantly refer to their falsely dichotomized functions, just as a reminder—“the cognitive dlPFC” and “the emotional vmPFC.” Or here’s a mnemonic—“dl” of the cognitive dlPFC standing for “deliberative,” the “vm” of the emotional vmPFC as “very (e)motional.” Lame, but it’s saved me on a few occasions.

  * Moreover, dlPFC patients are poor at the difficult task of taking someone else’s perspective. This is a subtype of something called Theory of Mind, and involves interactions between the dlPFC and a brain region called the temporoparietal juncture. More in a later chapter.

  * A reminder—as with all good studies of individuals with damage to particular brain regions, not only is there a control comparison group of people with no brain damage, but there’s an additional control group of people with damage to other, unrelate
d parts of the brain.

  * For those who care, some of the strongest responses are found in a subregion of the vmPFC called the orbitofrontal cortex.

  * We will return to Greene’s subsequent “trolleyology” work at length in the chapter on morality. Broadly, it shows that the differing decisions pivot around (a) the personal/impersonal contrast between pulling a lever and pushing with your own hands, (b) the means/side effect contrast between the person’s death being a necessity and its being an unintentional by-product, (c) the psychological distance to the potential victim.

  * Given the circuitry of the PFC, the most probable sequence is activation of the dlPFC, then activation of the vmPFC, then inhibition of the amygdala.

  * And this extends to a metalevel of reappraisal, as Gross has shown that one mediator of treatment outcome when using CBT for social anxiety is the belief that one can effectively reappraise.

  * And then there are circumstances where the limbic system overwhelms the frontal cortex, where there is no such thing as a good decision, where each choice is worse than the other. Think about what is, for a parent, probably the most excruciating scene in all of cinema—in Sophie’s Choice, when Sophie must make the Choice, when, without warning, she has seconds to choose which of her two children lives, which dies. Making her bludgeoned, unimaginable choice requires her frontocortical neurons to send signals to her prefrontal cortex and on to her motor cortex—after all, she eventually says words and moves her hands, pushing one child forward. And the bidirectionality of the circuitry is shown by the fact that her limbic system, no doubt, was screaming in agony to the frontal cortex.

  * Consider individuals with “repressive” personalities. Such individuals have highly regimented affect and behavior—they’re not emotionally expressive and aren’t great at reading emotions in others. They like ordered, structured, predictable lives, can tell you what they’re having for dinner a week from Thursday, and complete everything on time. And they have elevated metabolism in the frontal cortex and elevated circulating levels of stress hormones, showing that it can be enormously stressful to construct a world in which nothing stressful ever occurs.

  * In humans activation of the dopaminergic system is typically assessed with functional imaging techniques like fMRI, which detect changes in metabolism in different parts of the brain. To be precise, while an increase in metabolic demands in these regions is typically due to neurons there having lots of (dopamine-releasing) action potentials, the two are not synonymous. Nonetheless, for simplicity I’m using “dopaminergic signaling increases,” “dopamine pathways activate,” “dopamine is released” interchangeably.

  * And, in a fact that hints at a world of sex differences, dopaminergic responses to sexually arousing visual stimuli are greater in men than in women. Remarkably, this difference isn’t specific to humans. Male rhesus monkeys will forgo the chance to drink water when thirsty in order to see pictures of—I’m not quite sure how else to say this—crotch shots of female rhesus monkeys (while not being interested in other rhesus-y pictures).

  * As an important point, study subjects were all female.

  * Remarkably, in a gambling paradigm where both outcomes result in a shock, after a while, getting the lesser of the two shocks begins to activate dopamine signaling.

  * The phenomenon reminds me of the terribly cynical observation of a dormmate in college, one with a long string of tumultuously disastrous relationships: “A relationship is the price you pay for the anticipation of it.”

  * This fact prompted Greene, in a conversation with me, to dryly note how Harvard’s budget projections incorporate the expectation that if they work hard enough, approximately 50 percent of junior faculty will receive tenure.

  * And as a great example of the happiness of pursuit, where the rewarding quality of something is as much in the process as in the end product, the mesolimbic dopamine system plays a key role in motivating maternal care in female rats.

  * Its name—raphe nucleus—is not essential.

  * An urban legend has persisted forever that Skinner raised his daughter in a giant Skinner box, where she learned to lever press away for all her needs. Naturally, according to the legend, when she grew up she went mad, committed suicide, sued him, tried to murder him, etc. All untrue.

  * When I was in college, Skinner came to my dorm once for dinner and gave an extraordinarily dogmatic talk afterward. This produced an odd thought on my part as I listened to him. “Wow, this guy is, like, a total Skinnerian.”

  * It’s obvious which tribe I root for, being some manner of ethologist myself (but just to take this paean down a notch, remember that one of ethology’s founders was the odious Konrad Lorenz). In an inspired move, the three founders of ethology—Lorenz, Niko Tinbergen, and Karl von Frisch—were awarded the Nobel Prize in Physiology or Medicine in 1973. The biomedical community was appalled. Giving the prize to guys with foot fungi, whose main research technique was looking through binoculars—what’s that got to do with medicine? Of the trio, Lorenz was the energetic self-promoter and flashy popularizer, Tinbergen, one of my heroes, was the deep thinker and amazing experimentalist, and von Frisch played electric bass and didn’t say much.

  * How would ethologists figure out what sensory information is pertinent to an animal? An example: Among gulls, the mother’s beak has a conspicuous red spot. When she brings food to the chicks, they peck at the beak, and Mom regurgitates the food. Here’s how Tinbergen proved that the red spot triggers the pecking behavior: A subtraction approach, where he’d paint over the red spot on birds; chicks no longer pecked. A replication approach, where he’d take a two-by-four, paint a red dot on it, and wave it over the nest; chicks would start pecking. Or super stimulation, where he’d paint a gigantic red dot on the mother’s beak; chicks would go berserk with the pecking. This approach now incorporates robotics, where ethologists have built, for example, robotic bees that infiltrate and fiendishly deceive bee colonies by dancing about nonexistent food sources, which the bees then fly off in search of.

  * A great example of interspecies cute responses: A significant factor in how much money people pledge to donate to help an endangered species is the relative size of the animal’s eyes. Big googly eyes loosen purse strings.

  * Unconscious cues aren’t always about faces and posture. Among closely matched teams or individual male athletic competitors, wearing a red jersey boosts performance. This has been shown in Olympic boxing, tae kwon do, and wrestling, for rugby and soccer teams, and when playing a virtual gladitorial computer game. It has been speculated to reflect the fact that in many species (e.g., mandrill monkeys and widow birds) male dominance displays involve flashing a red body part, where more testosterone equals more intense red. I’m dubious about the explanation, as it feels like cherry-picking examples from other species.

  * Findings like this should not be confused with the rationale behind the “Twinkie defense.” In 1978 San Francisco mayor George Moscone and city supervisor Harvey Milk—the first openly gay politician in California—were assassinated by Dan White, a disgruntled ex-supervisor. According to the common misconception, during his trial, White’s defense attorneys argued that his addiction to sugary junk food somehow impaired his judgment and self-control. In reality, the defense argued that White suffered from diminished capacity because of his depression, and his shift from a healthy diet to one of junk food was merely evidence of his depressed state.

  * One recent study demonstrates a pointed version of this—describing someone as “African American” evokes associations with higher levels of education and income than does describing them as “black.”

  * A recent study shows life-and-death consequences of linguistic cuing. For the same storm intensity, hurricanes arbitrarily given female names kill more people than do those with male names (names alternate between the two genders). Why? People unconsciously take male-named hurri
canes more seriously and are more likely to comply with evacuation orders. And this despite both male and female names being selected for their innocuousness—this isn’t comparing Hurricane Mary Poppins with Hurricane Vlad the Impaler.

  * For a horrifying, documented example of bystanders being at least as callous as the apartment dwellers were reputed to be, Google the case of the death of two-year-old Wang Yue.

  * In these studies the control situation is when subjects are in the presence of another man. And FYI, the presence of men has no such effects on the behavior of women.