NATURE–NURTURE
The fact that identical twins aren’t identical in every respect tells us
that genes aren’t the whole story. By comparing identical twins raised
together and identical twins raised apart, via adoption, psychologists can
further disentangle the influence of shared and unique environmental
effects. The shock result to come out of this kind of research is that
identical twins raised together are no more similar to each other than
identical twins raised apart. Similarly, a child adopted into a family ends
up no more similar to her adopted siblings than if he or she had been
raised in another family. Stated starkly, this research suggests that the
family environment plays little if any role in the shaping of a child’s
personality. Unique environmental effects, such as a child’s circle of
friends and their experiences at school, are far more influential.
This revelation was popularized in a controversial 1998 book by the
psychologist Judith Rich Harris called The Nurture Assumption: Why
Children Turn Out The Way They Do. For years, psychologists from Freud
onwards had assumed that parents play a powerful role in the shaping
of their children’s personalities, but here was compelling evidence that
Fear of snakes – it’s human nature
While mainstream psychology has tended to concentrate on ways that
people differ from one another – known as individual differences- anthropologists and evolutionary psychologists have documented
the characteristics that we have in common. Indeed, in his book
Human Universals (1991), the anthropologist Donald Brown lists over
one hundred physical and behavioural traits that are common to all
cultures, such as language, music and humour. Rather than being
learned, these behaviours are considered to be part of human nature.
Take the example of the fear or wariness of snakes. Of course, it is
possible to learn to fear virtually anything. But our evolved human
nature means that most of us are quicker to learn to fear snakes (and
spiders, heights, the dark, confined spaces and so on) than modern
threats, such as guns – a phenomenon known as prepared learning.
Back in the 1980s Edwin Cook and his colleagues conditioned partici-
pants to fear snakes and guns by repeatedly pairing them with a loud,
unpleasant noise. Despite the fact that a loud noise is more consistent
with the threat of a gun, the procedure led to a far deeper and longer-
lasting fear of snakes than guns. This is an example of human nature in
action. Snakes were obviously more of a threat to our ancestors than
yet-to-be-invented guns, and individuals quick to learn the threat of
snakes were more likely to pass on their genes, including an inclination
for snake wariness, to later generations.