Brain Rules (Updated and Expanded)

Harvard’s
president, for
Pete’s sake, when in 2005 he attributed girls’ lower math and science scores
to behavioral genetics, comments that cost him his job. The battle of the
sexes has existed for a very long time, illustrated by three quotes separated
by centuries:
“The female is an impotent male, incapable of making semen because of the
coldness of her nature. We therefore should look upon the female state as if
it were a deformity, though one that occurs in the ordinary course of
nature.”
Aristotle (384–332 BC)
“Girls begin to talk and to stand on their feet sooner than boys because
weeds always grow up more quickly than good crops.”
Martin Luther (1483–1546)
“If they can put a man on the moon … why can’t they put them all there?”
Jill (graffiti I saw on a bathroom wall in 1985, in response to Luther’s quote
scribbled there)

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Almost 2,400 years of history separate Aristotle from Jill, yet we seem
to have barely moved. Invoking planet metaphors like Venus and Mars,
some purport to expand perceived differences into prescriptions for
relationships. And this is the most scientifically progressive era in human
history.
Mostly, I think, it comes down to statistics. When people hear about
measurable differences, they often think scientists are talking about
individuals, such as themselves. That’s a 
big
mistake. When scientists look
for behavioral trends, they do not look at individuals. They look at
populations. Trends emerge, but the many variations and overlaps mean that
statistics in these studies can never apply to individuals. There may very
well be differences in the way men and women think about some things.
But exactly how that relates to your behavior is a completely separate
question.
Mental disorders
Brain pathologies represent one of the strongest pieces of evidence that
sex chromosomes are involved in brain function and thus brain behavior.
Mental retardation is more common in males than in females in the general
population. Many of these pathologies are caused by mutations in any one
of 24 genes in the X chromosome. As you know, males have no backup X.
If their X gets damaged, they have to live with the consequences. If a
female’s X is damaged, she can often ignore the consequences.
Mental-health professionals have known for years about sex-based
differences in the type and severity of psychiatric disorders. Males are more
severely afflicted by schizophrenia than females, for example. By more than
two to one, women are more likely to get depressed than men, a figure that
shows up just after puberty and remains stable for the next 50 years. Males
have a greater tendency to be antisocial. Females have more anxiety. Most
alcoholics and drug addicts are male. Most anorexics are female. Says
Thomas Insel, from the National Institute of Mental Health, “It’s pretty
difficult to find any single factor that’s more predictive for some of these
disorders than gender.”
Emotions and stress

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It’s a horrible slide show. In it, a little boy is run over by a car while
walking with his parents. If you ever see that show, you will never forget it.
But what if you 
could
forget it? The brain’s amygdala aids in the creation of
emotions and our ability to remember them. Suppose there was a magic
elixir that could momentarily suppress it? Such an elixir does exist, and it
was used to show that men and women process emotions differently.
You have probably heard the term left brain versus right brain. You may
have heard that this underscores creative versus analytical people. That’s a
folk tale, the equivalent of saying the left side of a luxury liner is
responsible for keeping the ship afloat, and the right is responsible for
making it move through the water. Both sides are involved in both
processes. That doesn’t mean the hemispheres are equal, however. The right
side of the brain tends to remember the gist of an experience, and the left
brain tends to remember the details.
Researcher Larry Cahill eavesdropped on men’s and women’s brains
under acute stress (he showed them slasher films), and what he found is
this: Men handled the experience by firing up the amygdala in their brain’s
right hemisphere. Their left was comparatively silent. Women handled the
experience with the opposite hemisphere. Their left amygdala lit up, their
right comparatively silent. If males are firing up the side in charge of gist,
does that mean males remember more gist than detail of a given emotional
experience related to stress? Conversely, do females remember more detail
than gist? Cahill decided to find out.
That magic elixir of forgetting, a drug called propranolol, normally is
used to regulate blood pressure. As a beta-blocker, it also inhibits the
biochemistry that activates the amygdala during emotional experiences. The
drug is being investigated as a potential treatment for combat-related
disorders.
But Cahill gave it to his subjects before they watched a traumatic film.
One week later, he tested their memories of it. Sure enough, the men lost
the ability to recall the gist of the story, compared with men who didn’t take
the drug. Women lost the ability to recall the details. One must be careful
not to overinterpret these data. The results clearly define only emotional
responses to stressful situations, not objective details and summaries. This
is not a battle between the accountants and the visionaries.

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Cahill’s results come on the heels of similar findings around the world.
Other labs have extended his work, finding that women recall more
emotional autobiographical events, more rapidly and with greater intensity,
than men do. Women consistently report more vivid memories for
emotionally important events such as a recent argument, a first date, or a
vacation. Other studies show that, under stress, women tend to focus on
nurturing their offspring, while men tend to withdraw. This tendency in
females has sometimes been called “tend and befriend.” Is this caused by
nature or nurture? As Stephen Jay Gould says, “It is logically,
mathematically, and philosophically impossible to pull them apart.”
Verbal communication
Over the past several decades, behaviorist Deborah Tannen and others have
done some fascinating work on how men and women communicate
verbally. The CliffsNotes version of their findings: Women are better at it.
Women tend to use both hemispheres when speaking and processing
verbal information. Men primarily use one. Women tend to have thick
cables connecting their two hemispheres. Men’s are thinner. It’s as though
females have a backup system that males don’t. Researchers think these
neuroanatomical differences may explain why language and reading
disorders occur approximately twice as often in little boys as in little girls.
Women also recover from stroke-induced verbal impairment better than
men.
Girls seem verbally more sophisticated than little boys as they go
through the school system. They are better at verbal memory tasks, verbal
fluency tasks, and speed of articulation. When these little girls grow up,
they are still champions at processing verbal information. Real as these data
seem, however, almost none of them can be divorced from a social context.
That’s why Gould’s comment is so helpful.
Tannen spent years observing and videotaping how little girls and little
boys interact, especially when talking to their best friends. If any detectable
patterns emerged in children, she wanted to know if they also showed up in
college students. The patterns she found were both predictable and stable.
The conversational styles we develop as adults come directly from the
same-sex interactions we solidified as children. Tannen’s findings center on

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how boys and girls cement relationships and negotiate status within same-
sex groups, and then how these entrenched styles clash as men and women
try to communicate with one another as adults.