Quotes from Robert M. Sapolsky

Remarkably, the fetal brain generates far more neurons than are found in the adult. Why? During late fetal development, there is a dramatic competition in much of the brain, with winning neurons being the ones that migrate to the correct location and maximize synaptic connections to other neurons. And neurons that don't make the grade? They undergo "programmed cell death"—genes are activated that cause them to shrivel and die, their materials then recycled.

Men with more "masculine" 2D:4D ratios tend toward higher levels of aggression and math scores; more assertive personalities; higher rates of ADHD and autism (diseases with strong male biases); and decreased risk of depression and anxiety (disorders with a female skew). The faces and handwriting of such men are judged to be more "masculine." Furthermore, some reports show a decreased likelihood of being gay.

Perhaps fifty years since we learned that reading problems of a type that we now call dyslexia aren't due to laziness but instead involve microscopic cortical malformations.

If you're working to restrict your food intake, a milkshake just makes you want another one.

It is never really the case that stress makes you sick, or even increases your risk of being sick. Stress increases your risk of getting diseases that make you sick, or if you have such a disease, stress increases the risk of your defenses being overwhelmed by the disease.

The opposite of love is not hate; its opposite is indifference." The biologies of strong love and strong hate are similar in many ways, as we'll see.

This level is egoistic in that rules and their application come from within and reflect conscience, where a transgression exacts the ultimate cost—having to live with yourself afterward. It recognizes that being good and being law-abiding aren't synonymous.

In another study subjects waited an unknown length of time to receive a shock.12 This lack of predictability and control was so aversive that many chose to receive a stronger shock immediately. And

sometimes, it can be enormously stressful to construct a world without stressors.

Parts of the book describe work carried out in my own laboratory, and these studies have been made possible by funding from the National Institutes of Health, the National Institute of Mental Health, the National Science Foundation, the Sloan Foundation, the Klingenstein Fund, the Alzheimer's Association, and the Adler Foundation.

As you study the trait in more environments, the heritability score will decrease. This is recognized by Bouchard: "These conclusions [derived from a behavior genetics study] can be generalized, of course only to new populations exposed to a range of environments similar to those studied."31

The explains why basal levels of testosterone have little to do with subsequent aggression, and why increases in testosterone due to puberty, sexual stimulation, or the start of mating season don't increase aggression either.

Infuse oxytocin into the brain of a virgin rat, and she'll act maternally—retrieving, grooming, and licking pups. Block the actions of oxytocin in a rodent mother,*23 and she'll stop maternal behaviors, including nursing. Oxytocin

John Archer in a definitive 2006 review, "There is a weak and inconsistent association between testosterone levels and aggression in [human] adults, and … administration of testosterone to volunteers typically does not increase their aggression." The brain doesn't pay attention to fluctuations of testosterone levels within the normal range.

glucocorticoids in

maintaining the high rank is about social intelligence and impulse control: knowing which provocations to ignore and which coalitions to form, understanding other individuals' actions.

If it's the right person tickling you in that adolescent stage of being on the cusp of sexuality, maybe, just maybe, that tickling is going to be followed by something really good, like hand-holding. In contrast, if it's Slobodan Milosovic who is tickling you, maybe, just maybe, it will be followed up by his trying to ethnically cleanse you.

the worst stress-related health typically occurs in middle management, with its killer combo of high work demands but little autonomy—responsibility without control.

Remarkably, the size of neurons' dendritic trees in the hippocampus expands and contracts like an accordion throughout a female rat's ovulatory cycle, with the size (and her cognitive skills) peaking when estrogen peaks.fn6 Thus, neurons can form new dendritic branches and spines, increasing the size of their dendritic tree or, in other circumstances, do the opposite; hormones frequently mediate these effects.

In other words, the more genomically complex the organism, the larger the percentage of the genome devoted to gene regulation by the environment.

A chicken is an egg's way of making another egg

The candidate gene approaches show that the effect of a single gene on a behavior is typically tiny. In other words, having the "warrior gene" variant of MAO probably has less effect on your behavior than does believing that you have it.

What does the frontal cortex do? Its list of expertise includes working memory, executive function (organizing knowledge strategically, and then initiating an action based on an executive decision), gratification postponement, long-term planning, regulation of emotions, and reining in impulsivity.35

The biologies of strong love and strong hate are similar in many ways, as we'll see.