## Behave ### Behave  #### Metadata * Author: [[Robert M. Sapolsky]] * Full Title: Behave * Category: #books #### Highlights * I've had versions of this fantasy since I was a kid. Still do at times. And when I really immerse myself in it, my heart rate quickens, I flush, my fists clench. All those plans for Hitler, the most evil person in history, the soul most deserving of punishment. (Location 77) * To preach from an obvious soapbox, our species has problems with violence. We have the means to create thousands of mushroom clouds; shower heads and subway ventilation systems have carried poison gas, letters have carried anthrax, passenger planes have become weapons; mass rapes can constitute a military strategy; bombs go off in markets, schoolchildren with guns massacre other children; there are neighborhoods where everyone from pizza delivery guys to firefighters fears for their safety. And there are the subtler versions of violence—say, a childhood of growing up abused, or the effects on a minority people when the symbols of the majority shout domination and menace. (Location 86) * Our conversations are filled with military metaphors—we rally the troops after our ideas get shot down. (Location 97) * chess—"Kasparov kept pressing for a murderous attack. Toward the end, Kasparov had to oppose threats of violence with more of the same." (Location 99) * This book explores the biology of violence, aggression, and competition—the behaviors and the impulses behind them, the acts of individuals, groups, and states, and when these are bad or good things. It is a book about the ways in which humans harm one another. But it is also a book about the ways in which people do the opposite. What does biology teach us about cooperation, affiliation, reconciliation, empathy, and altruism? (Location 104) * I make my living as a combination neurobiologist—someone who studies the brain—and primatologist—someone who studies monkeys and apes. Therefore, this is a book that is rooted in science, specifically biology. (Location 118) * For example, the visual spectrum is a continuum of wavelengths from violet to red, and it is arbitrary where boundaries are put for different color names (for example, where we see a transition from "blue" to "green"); as proof of this, different languages arbitrarily split up the visual spectrum at different points in coming up with the words for different colors. Show someone two roughly similar colors. If the color-name boundary in that person's language happens to fall between the two colors, the person will overestimate the difference between the two. If the colors fall in the same category, the opposite happens. In other words, when you think categorically, you have trouble seeing how similar or different two things are. If you pay lots of attention to where boundaries are, you pay less attention to complete pictures. (Location 144) * There are not different disciplinary buckets. Instead, each one is the end product of all the biological influences that came before it and will influence all the factors that follow it. Thus, it is impossible to conclude that a behavior is caused by a gene, a hormone, a childhood trauma, because the second you invoke one type of explanation, you are de facto invoking them all. (Location 171) * Normal psychic life depends upon the good functioning of brain synapses, and mental disorders appear as a result of synaptic derangements. . . . It is necessary to alter these synaptic adjustments and change the paths chosen by the impulses in their constant passage so as to modify the corresponding ideas and force thought into different channels.5 (Location 192) * These were the words of the Portuguese neurologist Egas Moniz, around the time he was awarded the Nobel Prize in 1949 for his development of frontal leukotomies. Here was an individual pathologically stuck in a bucket having to do with a crude version of the nervous system. Just tweak those microscopic synapses with a big ol' ice pick (as was done once leukotomies, later renamed frontal lobotomies, became an assembly line operation). (Location 195) * The immensely high reproduction rate in the moral imbecile has long been established. . . . Socially inferior human material is enabled . . . to penetrate and finally to annihilate the healthy nation. The selection for toughness, heroism, social utility . . . must be accomplished by some human institution if mankind, in default of selective factors, is not to be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished much in this respect. We must—and should—rely on the healthy feelings of our Best and charge them . . . with the extermination of elements of the population loaded with dregs.6 This was Konrad Lorenz, animal behaviorist, Nobel laureate, cofounder of the field of ethology (stay tuned), regular on nature TV programs.7 Grandfatherly Konrad, in his Austrian shorts and suspenders, being followed by his imprinted baby geese, was also a rabid Nazi propagandist. Lorenz joined the Nazi Party the instant Austrians were eligible, and joined the party's Office of Race Policy, working to psychologically screen Poles of mixed Polish/German parentage, helping to determine which were sufficiently Germanized to be spared death. Here was a man pathologically mired in an imaginary bucket related to gross misinterpretations of what genes do. (Location 199) * House two female rats together, and over the course of weeks they will synchronize their reproductive cycles so that they wind up ovulating within a few hours of each other. Try the same with two human females (as reported in some but not all studies), and something similar occurs. It's called the Wellesley effect, first shown with roommates at all-women's Wellesley College.8 And when it comes to violence, we can be just like some other apes—we pummel, we cudgel, we throw rocks, we kill with our bare hands. (Location 219) * Finally, sometimes the only way to understand our humanness is to consider solely humans, because the things we do are unique. While a few other species have regular nonreproductive sex, we're the only ones to talk afterward about how it was. (Location 228) * After a few minutes the guy's driving evasively, but my wife's on him. Finally both cars stop at a red light, one that we know is a long one. Another car is stopped in front of the villain. He's not going anywhere. Suddenly my wife grabs something from the front seat divider, opens her door, and says, "Now he's going to be sorry." I rouse myself feebly—"Uh, honey, do you really think this is such a goo—" But she's out of the car, starts pounding on his window. I hurry over just in time to hear my wife say, "If you could do something that mean to another person, you probably need this," in a venomous voice. She then flings something in the window. She returns to the car triumphant, just glorious. "What did you throw in there!?" She's not talking yet. The light turns green, there's no one behind us, and we just sit there. The thug's car starts to blink a very sensible turn indicator, makes a slow turn, and heads down a side street into the dark at, like, five miles an hour. If it's possible for a car to look ashamed, this car was doing it. "Honey, what did you throw in there, tell me?" She allows herself a small, malicious grin. "A grape lollipop." I was awed by her savage passive-aggressiveness—"You're such a mean, awful human that something must have gone really wrong in your childhood, and maybe this lollipop will help correct that just a little." That guy was going to think twice before screwing with us again. I swelled with pride and love. (Location 239) * And the second example: In the mid-1960s, a rightist military coup overthrew the government of Indonesia, instituting the thirty-year dictatorship of Suharto known as the New Order. Following the coup, government-sponsored purges of communists, leftists, intellectuals, unionists, and ethnic Chinese left about a half million dead.9 Mass executions, torture, villages torched with inhabitants trapped inside. V. S. Naipaul, in his book Among the Believers: An Islamic Journey, describes hearing rumors while in Indonesia that when a paramilitary group would arrive to exterminate every person in some village, they would, incongruously, bring along a traditional gamelan orchestra. Eventually Naipaul encountered an unrepentant veteran of a massacre, and he asked him about the rumor. Yes, it is true. We would bring along gamelan musicians, singers, flutes, gongs, the whole shebang. Why? Why would you possibly do that? The man looked puzzled and gave what seemed to him a self-evident answer: "Well, to make it more beautiful." Bamboo flutes, burning villages, the lollipop ballistics of maternal love. We have our work cut out for us, trying to understand the virtuosity with which we humans harm or care for one another, and (Location 250) * We have our strategy in place. A behavior has occurred—one that is reprehensible, or wonderful, or floating ambiguously in between. What occurred in the prior second that triggered the behavior? This is the province of the nervous system. What occurred in the prior seconds to minutes that triggered the nervous system to produce that behavior? This is the world of sensory stimuli, much of it sensed unconsciously. What occurred in the prior hours to days to change the sensitivity of the nervous system to such stimuli? Acute actions of hormones. And so on, all the way back to the evolutionary pressures played out over the prior millions of years that started the ball rolling. (Location 261) * Let's examine this with respect to different types of "aggression."2 Animal behaviorists dichotomize between offensive and defensive aggression, distinguishing between, say, the intruder and the resident of a territory; the biology underlying these two versions differs. Such scientists also distinguish between conspecific aggression (between members of the same species) and fighting off a predator. Meanwhile, criminologists distinguish between impulsive and premeditated aggression. (Location 281) * When it comes to the more positive behaviors, the most pervasive issue is one that ultimately transcends semantics—does pure altruism actually exist? Can you ever separate doing good from the expectation of reciprocity, public acclaim, self-esteem, or the promise of paradise? (Location 303) * This speaks to an important point that runs through the book. As noted, we distinguish between hot-blooded and cold-blooded violence. We understand the former more, can see mitigating factors in it—consider the grieving, raging man who kills the killer of his child. (Location 310) * Note: Apple genius codebok * One scientist asked one of the monks whether he ever stops meditating because his knees hurt from all that cross-leggedness. He answered, "Sometimes I'll stop sooner than I planned, but not because it hurts; it's not something I notice. It's as an act of kindness to my knees." "Whoa," I thought, "these guys are from another planet." A cool, commendable one, but another planet nonetheless. Crimes of passion and good acts of passion make the most sense to us (nevertheless, as we shall see, dispassionate kindness often has much (Location 316) * This is shown in a subtle study.7 Subjects in a brain scanner entered a virtual room where they encountered either an injured person in need of help or a menacing extraterrestrial; subjects could either bandage or shoot the individual. Pulling a trigger and applying a bandage are different behaviors. But they are similar, insofar as bandaging the injured person and shooting the alien are both the "right" things. And contemplating those two different versions of doing the right thing activated the same circuitry in the most context-savvy part of the brain, the prefrontal cortex. (Location 325) * But on the most proximal level, in this chapter we ask: What happened one second before the behavior that caused it to occur? (Location 342) * This chapter is one of the book's anchors. The brain is the final common pathway, the conduit that mediates the influences of all the distal factors to be covered in the chapters to come. What happened an hour, a decade, a million years earlier? What happened were factors that impacted the brain and the behavior it produced. (Location 343) * The recently evolved layer of neocortex sitting on the upper surface of the brain. Proportionately, primates devote more of their brain to this layer than do other species. Cognition, memory storage, sensory processing, abstractions, philosophy, navel contemplation. Read a scary passage of a book, and layer 3 signals layer 2 to make you feel frightened, prompting layer 1 to initiate shivering. (Location 361) * The nervous system is about contrasts, unambiguous extremes between having something and having nothing to say, maximizing signal-to-noise ratios. And this is demanding and expensive.* (Location 10282) * In contrast, there are single neurons in the spinal cord that send out projection cables many feet long. There are spinal cord neurons in blue whales that are half the length of a basketball court. (Location 10297) * The ears, the inputs, are called dendrites. The output begins with a single long cable called an axon, which then ramifies into axonal endings—these axon terminals are the mouths (ignore the myelin sheath for the moment). Those axon terminals connect to the dendrites of the next neuron in line. Thus a neuron's dendritic ears are informed that the neuron behind it is excited. The flow of information then sweeps from the dendrites to the cell body to the axon to the axon terminals, and is then passed to the next neuron. (Location 10303) * You couldn't ask for a more dramatic contrast: I have nothing to say = inside of the neuron is negatively charged. I have something to say = inside is positive. No neuron ever confuses the two. The internally negative state is called the "resting potential." (Location 10320) * The excited state is called the "action potential." And why is generating this dramatic resting potential such an active process? (Location 10322) * And out of this comes a rule: the more neurons that neuron A projects to, by definition, the more neurons it can influence; however, the more neurons it projects to, the smaller its average influence will be at each of those target neurons. There's a trade-off. (Location 10371) * Now to put in a flabbergasting real number—your average neuron has about ten thousand dendritic spines and about the same number of axon terminals. Factor in a hundred billion neurons, and you see why brains, rather than kidneys, write poetry. (Location 10378) * experience, and other factors filling this book's pages. We've now made it from one end of a neuron to the other. How exactly does a neuron with an action potential communicate its excitation to the next neuron in line? (Location 10385) * But as another possibility, you could decrease the activity of the reuptake pump. As a result, less of the neurotransmitter is removed from the synapse. Thus it sticks around longer and binds to the receptors repeatedly, amplifying the signal. Or, as the conceptual equivalent, you could decrease the activity of the degradative enzyme; less neurotransmitter is broken down, so more sticks around longer in the synapse, having an enhanced effect. As we saw, some of the most interesting findings that help explain individual differences in the behaviors that concern us in this book relate to amounts of neurotransmitter made and released, and the amounts and functioning of the receptors, reuptake pumps, and degradative enzymes. (Location 10430) * There are dozens of neurotransmitters that have been identified. Some of the most renowned: serotonin, norepinephrine, dopamine, acetylcholine, glutamate (the most excitatory neurotransmitter in the brain), and GABA (the most inhibitory). (Location 10454) * You do not ever want to find yourself running for your life from a lion and, oopsies, the neurons that tell your muscles to run fast go off-line because they've run out of neurotransmitter. Neurotransmitters are therefore made from precursors that are plentiful; often they are simple dietary constituents. Serotonin and dopamine, for example, are made from the dietary amino acids tryptophan and tyrosine, respectively. Acetylcholine is made from dietary choline and lecithin. (Location 10458) * neurotransmitter, prolonging its effects in the synapse. The modern antidepressant of choice, Prozac, does exactly that in serotonin synapses. Thus it is often referred to as an "SSRI"—a selective serotonin reuptake inhibitor. (Location 10480) # Behave  ## Metadata - Author: [[Robert M. Sapolsky]] - Full Title: Behave - Category: #books ## Highlights - I’ve had versions of this fantasy since I was a kid. Still do at times. And when I really immerse myself in it, my heart rate quickens, I flush, my fists clench. All those plans for Hitler, the most evil person in history, the soul most deserving of punishment. (Location 77) - To preach from an obvious soapbox, our species has problems with violence. We have the means to create thousands of mushroom clouds; shower heads and subway ventilation systems have carried poison gas, letters have carried anthrax, passenger planes have become weapons; mass rapes can constitute a military strategy; bombs go off in markets, schoolchildren with guns massacre other children; there are neighborhoods where everyone from pizza delivery guys to firefighters fears for their safety. And there are the subtler versions of violence—say, a childhood of growing up abused, or the effects on a minority people when the symbols of the majority shout domination and menace. (Location 86) - Our conversations are filled with military metaphors—we rally the troops after our ideas get shot down. (Location 97) - chess—“Kasparov kept pressing for a murderous attack. Toward the end, Kasparov had to oppose threats of violence with more of the same.” (Location 99) - This book explores the biology of violence, aggression, and competition—the behaviors and the impulses behind them, the acts of individuals, groups, and states, and when these are bad or good things. It is a book about the ways in which humans harm one another. But it is also a book about the ways in which people do the opposite. What does biology teach us about cooperation, affiliation, reconciliation, empathy, and altruism? (Location 104) - I make my living as a combination neurobiologist—someone who studies the brain—and primatologist—someone who studies monkeys and apes. Therefore, this is a book that is rooted in science, specifically biology. (Location 118) - For example, the visual spectrum is a continuum of wavelengths from violet to red, and it is arbitrary where boundaries are put for different color names (for example, where we see a transition from “blue” to “green”); as proof of this, different languages arbitrarily split up the visual spectrum at different points in coming up with the words for different colors. Show someone two roughly similar colors. If the color-name boundary in that person’s language happens to fall between the two colors, the person will overestimate the difference between the two. If the colors fall in the same category, the opposite happens. In other words, when you think categorically, you have trouble seeing how similar or different two things are. If you pay lots of attention to where boundaries are, you pay less attention to complete pictures. (Location 144) - There are not different disciplinary buckets. Instead, each one is the end product of all the biological influences that came before it and will influence all the factors that follow it. Thus, it is impossible to conclude that a behavior is caused by a gene, a hormone, a childhood trauma, because the second you invoke one type of explanation, you are de facto invoking them all. (Location 171) - Normal psychic life depends upon the good functioning of brain synapses, and mental disorders appear as a result of synaptic derangements. . . . It is necessary to alter these synaptic adjustments and change the paths chosen by the impulses in their constant passage so as to modify the corresponding ideas and force thought into different channels.5 (Location 192) - These were the words of the Portuguese neurologist Egas Moniz, around the time he was awarded the Nobel Prize in 1949 for his development of frontal leukotomies. Here was an individual pathologically stuck in a bucket having to do with a crude version of the nervous system. Just tweak those microscopic synapses with a big ol’ ice pick (as was done once leukotomies, later renamed frontal lobotomies, became an assembly line operation). (Location 195) - The immensely high reproduction rate in the moral imbecile has long been established. . . . Socially inferior human material is enabled . . . to penetrate and finally to annihilate the healthy nation. The selection for toughness, heroism, social utility . . . must be accomplished by some human institution if mankind, in default of selective factors, is not to be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished much in this respect. We must—and should—rely on the healthy feelings of our Best and charge them . . . with the extermination of elements of the population loaded with dregs.6 This was Konrad Lorenz, animal behaviorist, Nobel laureate, cofounder of the field of ethology (stay tuned), regular on nature TV programs.7 Grandfatherly Konrad, in his Austrian shorts and suspenders, being followed by his imprinted baby geese, was also a rabid Nazi propagandist. Lorenz joined the Nazi Party the instant Austrians were eligible, and joined the party’s Office of Race Policy, working to psychologically screen Poles of mixed Polish/German parentage, helping to determine which were sufficiently Germanized to be spared death. Here was a man pathologically mired in an imaginary bucket related to gross misinterpretations of what genes do. (Location 199) - House two female rats together, and over the course of weeks they will synchronize their reproductive cycles so that they wind up ovulating within a few hours of each other. Try the same with two human females (as reported in some but not all studies), and something similar occurs. It’s called the Wellesley effect, first shown with roommates at all-women’s Wellesley College.8 And when it comes to violence, we can be just like some other apes—we pummel, we cudgel, we throw rocks, we kill with our bare hands. (Location 219) - Finally, sometimes the only way to understand our humanness is to consider solely humans, because the things we do are unique. While a few other species have regular nonreproductive sex, we’re the only ones to talk afterward about how it was. (Location 228) - After a few minutes the guy’s driving evasively, but my wife’s on him. Finally both cars stop at a red light, one that we know is a long one. Another car is stopped in front of the villain. He’s not going anywhere. Suddenly my wife grabs something from the front seat divider, opens her door, and says, “Now he’s going to be sorry.” I rouse myself feebly—“Uh, honey, do you really think this is such a goo—” But she’s out of the car, starts pounding on his window. I hurry over just in time to hear my wife say, “If you could do something that mean to another person, you probably need this,” in a venomous voice. She then flings something in the window. She returns to the car triumphant, just glorious. “What did you throw in there!?” She’s not talking yet. The light turns green, there’s no one behind us, and we just sit there. The thug’s car starts to blink a very sensible turn indicator, makes a slow turn, and heads down a side street into the dark at, like, five miles an hour. If it’s possible for a car to look ashamed, this car was doing it. “Honey, what did you throw in there, tell me?” She allows herself a small, malicious grin. “A grape lollipop.” I was awed by her savage passive-aggressiveness—“You’re such a mean, awful human that something must have gone really wrong in your childhood, and maybe this lollipop will help correct that just a little.” That guy was going to think twice before screwing with us again. I swelled with pride and love. (Location 239) - And the second example: In the mid-1960s, a rightist military coup overthrew the government of Indonesia, instituting the thirty-year dictatorship of Suharto known as the New Order. Following the coup, government-sponsored purges of communists, leftists, intellectuals, unionists, and ethnic Chinese left about a half million dead.9 Mass executions, torture, villages torched with inhabitants trapped inside. V. S. Naipaul, in his book Among the Believers: An Islamic Journey, describes hearing rumors while in Indonesia that when a paramilitary group would arrive to exterminate every person in some village, they would, incongruously, bring along a traditional gamelan orchestra. Eventually Naipaul encountered an unrepentant veteran of a massacre, and he asked him about the rumor. Yes, it is true. We would bring along gamelan musicians, singers, flutes, gongs, the whole shebang. Why? Why would you possibly do that? The man looked puzzled and gave what seemed to him a self-evident answer: “Well, to make it more beautiful.” Bamboo flutes, burning villages, the lollipop ballistics of maternal love. We have our work cut out for us, trying to understand the virtuosity with which we humans harm or care for one another, and (Location 250) - We have our strategy in place. A behavior has occurred—one that is reprehensible, or wonderful, or floating ambiguously in between. What occurred in the prior second that triggered the behavior? This is the province of the nervous system. What occurred in the prior seconds to minutes that triggered the nervous system to produce that behavior? This is the world of sensory stimuli, much of it sensed unconsciously. What occurred in the prior hours to days to change the sensitivity of the nervous system to such stimuli? Acute actions of hormones. And so on, all the way back to the evolutionary pressures played out over the prior millions of years that started the ball rolling. (Location 261) - Let’s examine this with respect to different types of “aggression.”2 Animal behaviorists dichotomize between offensive and defensive aggression, distinguishing between, say, the intruder and the resident of a territory; the biology underlying these two versions differs. Such scientists also distinguish between conspecific aggression (between members of the same species) and fighting off a predator. Meanwhile, criminologists distinguish between impulsive and premeditated aggression. (Location 281) - When it comes to the more positive behaviors, the most pervasive issue is one that ultimately transcends semantics—does pure altruism actually exist? Can you ever separate doing good from the expectation of reciprocity, public acclaim, self-esteem, or the promise of paradise? (Location 303) - This speaks to an important point that runs through the book. As noted, we distinguish between hot-blooded and cold-blooded violence. We understand the former more, can see mitigating factors in it—consider the grieving, raging man who kills the killer of his child. (Location 310) - Note: Apple genius codebok - One scientist asked one of the monks whether he ever stops meditating because his knees hurt from all that cross-leggedness. He answered, “Sometimes I’ll stop sooner than I planned, but not because it hurts; it’s not something I notice. It’s as an act of kindness to my knees.” “Whoa,” I thought, “these guys are from another planet.” A cool, commendable one, but another planet nonetheless. Crimes of passion and good acts of passion make the most sense to us (nevertheless, as we shall see, dispassionate kindness often has much (Location 316) - This is shown in a subtle study.7 Subjects in a brain scanner entered a virtual room where they encountered either an injured person in need of help or a menacing extraterrestrial; subjects could either bandage or shoot the individual. Pulling a trigger and applying a bandage are different behaviors. But they are similar, insofar as bandaging the injured person and shooting the alien are both the “right” things. And contemplating those two different versions of doing the right thing activated the same circuitry in the most context-savvy part of the brain, the prefrontal cortex. (Location 325) - But on the most proximal level, in this chapter we ask: What happened one second before the behavior that caused it to occur? (Location 342) - This chapter is one of the book’s anchors. The brain is the final common pathway, the conduit that mediates the influences of all the distal factors to be covered in the chapters to come. What happened an hour, a decade, a million years earlier? What happened were factors that impacted the brain and the behavior it produced. (Location 343) - The recently evolved layer of neocortex sitting on the upper surface of the brain. Proportionately, primates devote more of their brain to this layer than do other species. Cognition, memory storage, sensory processing, abstractions, philosophy, navel contemplation. Read a scary passage of a book, and layer 3 signals layer 2 to make you feel frightened, prompting layer 1 to initiate shivering. (Location 361) - The nervous system is about contrasts, unambiguous extremes between having something and having nothing to say, maximizing signal-to-noise ratios. And this is demanding and expensive.* (Location 10282) - In contrast, there are single neurons in the spinal cord that send out projection cables many feet long. There are spinal cord neurons in blue whales that are half the length of a basketball court. (Location 10297) - The ears, the inputs, are called dendrites. The output begins with a single long cable called an axon, which then ramifies into axonal endings—these axon terminals are the mouths (ignore the myelin sheath for the moment). Those axon terminals connect to the dendrites of the next neuron in line. Thus a neuron’s dendritic ears are informed that the neuron behind it is excited. The flow of information then sweeps from the dendrites to the cell body to the axon to the axon terminals, and is then passed to the next neuron. (Location 10303) - You couldn’t ask for a more dramatic contrast: I have nothing to say = inside of the neuron is negatively charged. I have something to say = inside is positive. No neuron ever confuses the two. The internally negative state is called the “resting potential.” (Location 10320) - The excited state is called the “action potential.” And why is generating this dramatic resting potential such an active process? (Location 10322) - And out of this comes a rule: the more neurons that neuron A projects to, by definition, the more neurons it can influence; however, the more neurons it projects to, the smaller its average influence will be at each of those target neurons. There’s a trade-off. (Location 10371) - Now to put in a flabbergasting real number—your average neuron has about ten thousand dendritic spines and about the same number of axon terminals. Factor in a hundred billion neurons, and you see why brains, rather than kidneys, write poetry. (Location 10378) - experience, and other factors filling this book’s pages. We’ve now made it from one end of a neuron to the other. How exactly does a neuron with an action potential communicate its excitation to the next neuron in line? (Location 10385) - But as another possibility, you could decrease the activity of the reuptake pump. As a result, less of the neurotransmitter is removed from the synapse. Thus it sticks around longer and binds to the receptors repeatedly, amplifying the signal. Or, as the conceptual equivalent, you could decrease the activity of the degradative enzyme; less neurotransmitter is broken down, so more sticks around longer in the synapse, having an enhanced effect. As we saw, some of the most interesting findings that help explain individual differences in the behaviors that concern us in this book relate to amounts of neurotransmitter made and released, and the amounts and functioning of the receptors, reuptake pumps, and degradative enzymes. (Location 10430) - There are dozens of neurotransmitters that have been identified. Some of the most renowned: serotonin, norepinephrine, dopamine, acetylcholine, glutamate (the most excitatory neurotransmitter in the brain), and GABA (the most inhibitory). (Location 10454) - You do not ever want to find yourself running for your life from a lion and, oopsies, the neurons that tell your muscles to run fast go off-line because they’ve run out of neurotransmitter. Neurotransmitters are therefore made from precursors that are plentiful; often they are simple dietary constituents. Serotonin and dopamine, for example, are made from the dietary amino acids tryptophan and tyrosine, respectively. Acetylcholine is made from dietary choline and lecithin. (Location 10458) - neurotransmitter, prolonging its effects in the synapse. The modern antidepressant of choice, Prozac, does exactly that in serotonin synapses. Thus it is often referred to as an “SSRI”—a selective serotonin reuptake inhibitor. (Location 10480)