All too human? Monkeys mimic children in toy
picks
WASHINGTON Just like human boys and girls, male monkeys like to
play with toy cars while female monkeys prefer dolls, a research
project has shown.
This intriguing discovery is one of many signs of deep-rooted
behavioral differences between the sexes that scientists are
exploring with the latest tools of genetics and neuroscience.
Researchers report significant differences in the structure and
functioning of male and female brains in humans and in animals
that show up in different behaviors.
The differences apparently date far back in evolutionary history to
the time before humans and monkeys separated from their common
ancestor about 25 million years ago, said Gerianne Alexander, a
psychologist at Texas A&M University in College Station, who
led the experiment published in the journal Evolution and Human
Behavior.
Researchers put a variety of toys in front of 44 male and 44 female
vervets, a breed of small African monkey, and measured the amount
of time they spent with each object.
Like little boys, some male monkeys moved a toy car along the
ground. Like little girls, female monkeys closely inspected a doll.
Males also preferred balls while females fancied cooking pots. Both
were equally interested in neutral objects such as a picture book
and a stuffed dog.
People used to think that boys and girls played differently because
of the way they were brought up. Now scientists such as Alexander
say a creature's genetic inheritance also plays an important
role.
"Vervet monkeys, like human beings, show sex differences in toy
preferences," Alexander wrote in the report. "Sex-related object
preference appeared early in human evolution."
Alexander speculated that females of both species prefer dolls
because evolution programmed them to care for infants. Males may
have evolved toy preferences that involve throwing and moving,
skills useful for hunting and for finding a mate.
Besides observing behavior, scientists are using the latest
brain-scanning techniques to examine what happens inside people's
heads when they are thinking or acting.
PET (positron emission tomography) and fMRI (functional magnetic
resonance imagery) scans light up in regions of the brain that are
most active while performing certain tasks. They have become a key
tool of modern brain research.
Many studies have shown that, in general, men tend to be better at
mathematics and spatial reasoning while women outdo men in verbal
and language skills.
For example, in a computerized maze-searching experiment, it took
women five minutes longer than men to find their way to a goal,
according to Scott Mowatt, a psychologist at Wayne State University
in Detroit. But women outperformed men in a test of verbal fluency
conducted by Wei-li Chang and colleagues at the National Institute
of Mental Health in Bethesda, Md.
"Human evolution has created two different types of brains designed
for equally intelligent behavior," Richard Haier, a neuroscientist
at the University of California, Irvine, wrote in the journal
NeuroImage.
Haier also reported a striking difference in the structure of male
and female brains. Men, he said, have much more gray matter in
areas dedicated to general intelligence. Women, on the other hand,
have far more white matter in those areas. Gray matter consists of
the clusters of brain cells, or neurons, that process information.
White matter refers to the network of specialized cells that
support and connect the processing centers. Both are necessary for
intelligence.
"Men and women apparently achieve similar IQ results with different
brain regions," Haier said.
