More on this book
Community
Kindle Notes & Highlights
Read between
February 11, 2024 - June 8, 2025
Peer socialization, with different peers modeling different behaviors with varying allure. The importance of peers has often been underappreciated by developmental psychologists but is no surprise to any primatologists.
the usual among primates is kids learning by watching their somewhat older peers.
Environmental influences. Is the neighborhood park safe? Are there more bookstores or liquor stores?
culture dramatically influences parenting style, the behaviors modeled by peers, the sorts of physical and social communities that are constructed.
whether kids aspire to earn lots of merit badges versus getting skilled at harassing out-group members.
a study examining more than a million people across China and the U.S. showed the effects of growing up in clement weather (i.e., mild fluctuations around an average of seventy degrees). Such individuals are, on the average, more individualistic, extroverted, and open to novel experience.
For example, lots of childhood stress, by way of glucocorticoids, impairs construction of the frontal cortex, producing an adult less adept at helpful things like impulse control. Lots of exposure to testosterone early in life makes for the construction of a highly reactive amygdala, producing an adult more likely to respond aggressively to provocation.
“epigenetics,” revealing how early life experience causes long-lasting changes in gene expression in particular brain regions. Now, this is not experience changing genes themselves (i.e., changing DNA sequences), but instead changing their regulation—whether some gene is always active, never active, or active in one context but not another;
Just to show the scale of epigenetic complexity, differences in mothering styles in monkeys cause epigenetic changes in more than a thousand genes expressed in the offspring’s frontal cortex.
how lucky was the childhood you were handed?
This field has produced a finding that should floor anyone holding out for free will. For every step higher in one’s ACE score, there is roughly a 35 percent increase in the likelihood of adult antisocial behavior, including violence; poor frontocortical-dependent cognition; problems with impulse control; substance abuse; teen pregnancy and unsafe sex and other risky behaviors; and increased vulnerability to depression and anxiety disorders. Oh, and also poorer health and earlier death.
Thus, essentially every aspect of your childhood—good, bad, or in between—factors over which you had no control, sculpted the adult brain you have
the likes of ACE scores are about adult potential and vulnerability, not inevitable destiny, and there are plenty of people whose adulthoods are radically different from what you’d expect, given their childhoods. This is just another piece of the sequence of influences.
Environmental influences begin long before birth. The biggest source of these influences is what’s in the maternal circulation, which will help determine what’s in the fetus—levels
Lots of glucocorticoids from Mom marinating your fetal brain, thanks to maternal stress, and there’s increased vulnerability to depression and anxiety in your adulthood. Lots of androgens in your fetal circulation (coming from Mom; females secrete androgens, though to a lesser extent than do males) makes you more likely as an adult of either sex to show spontaneous and reactive aggression, poor emotion regulation, low empathy, alcoholism, criminality, even lousy handwriting.
Genes have plenty to do with decision-making crossroads, and in more interesting ways than commonly believed.
Our bodies are filled with thousands of different types of proteins doing dizzyingly varied jobs.
Some are messengers—many neurotransmitters, hormones, and immune messengers are proteins.
virtually all receptors for messengers throughout the body are made of protein.
Each type of protein is constructed from a distinctive sequence of different types of amino acid building blocks; the sequence determines the shape of the protein; the shape determines function.
A “gene” is the stretch of DNA that specifies the sequence/shape/function of a particular protein. Each of our approximately twenty thousand genes codes f...
This highlight has been truncated due to consecutive passage length restrictions.
Saying that a gene decides when to generate its associated protein is like saying that the recipe decides when to bake the cake that it codes for. Instead, genes are turned on and off by environment. What is meant here by environment? It can be the environment within a single cell—a
Environment can encompass the entire body—a
Or environment can take the form of our everyday usage, namely events happening in the world around us. These different versions of environment are linked. For example, living in a stressful, dangerous city will produce chronically elevated levels of glucocorticoids secreted by your adrenal glands, which will activate particular genes in neurons in the amygdala, making those cells more excitable.[*24]
Not every stretch of DNA contributes to the code in a gene; instead, long stretches don’t code for anything. Instead, they are the on/off switches for activating nearby genes. Now for a wild fact—only about 5 percent of DNA constitutes genes. The remaining 95 percent? The dizzyingly complex on/off switches,
In other words, most DNA is devoted to gene regulation rather than to genes themselves. Moreover, evolutionary changes in DNA are usually more consequential when they alter on/off switches rather than the gene.
Genes code for workhorse proteins; genes don’t decide when they are active but are, instead, regulated by environmental signals; the evolution of DNA is disproportionately about gene regulation rather than about genes. So environmental signals have activated some gene, leading to the production of its protein; the newly made proteins then do their usual thing. As a next key point, the same protein can work differently in different environments.
When it comes to humans, it can be silly to ask what a particular gene does—only what it does in a particular environment.
Suppose someone has a gene variant related to aggression; depending on the environment, that can result in an increased likelihood of street brawling or of playing chess really aggressively.
And how can individual differences in gene variants contribute to differences in serotonin signaling? Easily—different flavors exist for the genes coding for the proteins that synthesize serotonin, that remove it from the synapse, and that degrade it,[*28] plus variants in the genes that code more than a dozen different types of serotonin receptors.[44]
There’s usually extensive individual variation in every relevant gene, and you weren’t consulted as to which you’d choose to inherit.
You get precisely what was discussed above, namely dramatically different effects of the gene variant depending on environment. For example, one variant of the gene whose protein breaks down serotonin will increase your risk of antisocial behavior…but only if you were severely abused during childhood. A variant of a dopamine receptor gene makes you either more or less likely to be generous, depending on whether you grew up with or without secure parental attachment. That same variant is associated with poor gratification postponement…if you were raised in poverty.
humans have roughly twenty thousand genes in our genome; of those, approximately 80 percent are active in the brain—sixteen thousand. Of those genes, nearly all come in more than one flavor (are “polymorphic”).
which adds up to there being individual variability in approximately four million spots in the sequence of DNA that codes for genes active in the brain.[*30],[47]
as a familiar theme, genes are about potentials and vulnerabilities, not inevitabilities, and the effects of most of these genes on behavior are relatively mild. Nonetheless, all these effects on behavior arise from genes you didn’t choose, interacting with a childhood you didn’t choose.[48]
from your moment of birth, you were subject to a universal, which is that every culture’s values include ways to make their inheritors recapitulate those values, to become “the sort of people you come from.”
Cultures produce dramatically different behaviors with consistent patterns. One of the most studied contrasts concerns “individualist” versus “collectivist” cultures.
Collectivist cultures, in contrast, espouse harmony, interdependence, and conformity, where the needs of the community guide behavior; the priority is that your actions make the community proud, because you are “theirs.”
The American goal is to distinguish yourself by getting ahead of everyone else; the East Asian is to avoid being distinguishable.[*31] And from these differences come major differences as to what count as norm violations and what you do about them.[49]
Thus, cultural differences arising centuries, millennia, ago, influence behaviors from the most subtle and minuscule to dramatic.[*33]
For various reasons, humans were sculpted by evolution over millions of years to be, on the average, more aggressive than bonobos but less so than chimps, more social than orangutans but less so than baboons, more monogamous than mouse lemurs but more polygamous than marmosets.
This is because evolving means changes in what variants of genes you find in organisms and thus the ways in which they shape brain construction. Study hormones and behavior, and we’re also studying what fetal life had to do with the development of the glands that secrete those hormones. So on and so on. Each moment flowing from all that came before.
Pete Alces, there is “no remaining gap between nature and nurture for moral responsibility to fill.”
This seamless stream shows why bad luck doesn’t get evened out, why it amplifies instead. Have some particular unlucky gene variant, and you’ll be unluckily sensitive to the effects of adversity during childhood. Suffering from early-life adversity is a predictor that you’ll be spending the rest of your life in environments that present you with fewer opportunities than most, and that enhanced developmental sensitivity will unluckily make you less able to benefit from rare opportunities that might arise, because you may not understand them, may not recognize them as opportunities, may not have
...more
show me that the thing a neuron just did in someone’s brain was unaffected by any of these preceding factors—by the goings-on in the eighty billion neurons surrounding it, by any of the infinite number of combinations of hormone levels percolated that morning, by any of the countless types of childhoods and fetal environments that could have been experienced, by any of the two to the four millionth power different genomes that neuron contains, multiplied by the nearly as large range of epigenetic orchestrations possible. Et cetera. All out of your control.
Why did that moment just occur? “Because of what came before it.” Then why did that moment just occur? “Because of what came before that,” forever,[*44] isn’t absurd and is, instead, how the universe works.
In order to prove there’s free will, you have to show that some behavior just happened out of thin air in the sense of considering all these biological precursors. It may be possible to sidestep that with some subtle philosophical arguments, but you can’t with anything known to science.
It is why it is anything but an absurdly high bar or straw man to say that free will can exist only if neurons’ actions are completely uninfluenced by all the uncontrollable factors that came before. It’s the only requirement there can be, because all that came before, with its varying flavors of uncontrollable luck, is what came to constitute you. This is how you became you.[59]
to repeat our emerging mantra, all we are is the history of our biology, over which we had no control, and of its interaction with environments, over which we also had no control, creating who we are in the moment.
it’s our guy with a neurodevelopmental disorder due to fetal neurotoxicity, repeated childhood trauma, substance abuse, repeated brain injuries, and a recent stabbing in a similar situation. His history has resulted in this part of his brain being enlarged, this other part atrophied, this pathway virtually disconnected. And as a result, there’s, like, zero chance that he’ll make a prudent, self-regulated decision in those eleven seconds. And you’d have done the same thing if life had handed you that brain.
