The Problems with “Nature vs. Nurture”
Plainly,
people differ from one another in their intelligence and their talents. But
what causes these differences? This question is often framed in terms of two
alternatives— the notion that what matters is genetics and heredity, or the
notion that what matters is environment (and so learning and experience). The
options, in other words, are boiled down to the dichotomy of “nature vs.
nurture.”
As
we discussed, however, this framing of the issue makes no sense, because the
influences of genes and environment are inevitably intertwined. Specifically,
someone’s genetic heritage merely establishes his genotype; the traits he ends up with (his phenotype) depend on how the process of development, guided by that
genotype, unfolds. That developmental process is, of course, heavily shaped by
genetic factors. But it is also powerfully influenced by the person’s
environment—what nutri-ents he’s exposed to, or what toxins; and, crucially,
what experiences he has. In short: There’s no such thing as genetic influences
independent of environment.
Likewise,
how someone benefits from experience depends on her capacity to per-ceive, to
understand, and to form memories. And these capacities depend on the biological
equipment that each person has—her eyes, for example, and her brain. This
biological equipment, in turn, is heavily shaped by the person’s genotype. As a
result, there’s no way for experience to influence us independent of genetics.
Even
with these points acknowledged, it’s clear that some traits are more directly
shaped by genetic influences than others. For example, the color of someone’s
eyes (assuming he’s not wearing tinted contact lenses) depends almost entirely
on the genetic pattern he has inherited. Conversely, the language that someone
speaks (French or Italian, Walbiri or Bantu) depends on where (and with whom)
she grows up. As it turns out, to the fact that someone can learn language at
all is heavily guided by genetics.
But the choice of language depends on
the environment, not on genes.
Where
does intelligence fall in this range from heavily influenced by genes (like eye
color is) to less influenced (like choice of language)? We took some steps
toward answering this question earily —and, as we saw there, the answer is
complicated: In some circumstances, genetic factors play a large role; in others,
genes count for less. And, as we’ll see, the role for genetic influences
depends on whether we’re asking why various individuals
perform differently on intelligence tests, or whether we’re asking why various groups (racial groups in particular)
perform differently on these tests. Let’s start by asking why various
individuals seem to have different levels of intelligence.
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