His and Hers Brains

STUDIES FIND DIFFERENCES IN MALE, FEMALE BRAINS

Author(s):    Allan R. Andrews Globe Staff

Date: April 22, 1981 Section: RUN OF PAPER

On the towel rack that we call our anatomy, nature appears to have hung his-and-hers brains.

But whether those differences should be regarded as significant remains an open question.

Sensitized by the potential for sexist implications, biologists and psychologists studying sex differences in the brain and in human behavior are cautious and divided on their interpretations of evidence suggesting that the female brain is put together differently than the male brain, and that women use their brains differently than do men.

"I won't make any prounouncements one way or the other," said Dr. Peter Wolff of Children's Hospital Medical Center on the social implications of his research that shows, for example, that growing females are more proficient at tasks requiring the use of small motor muscles.

This proficiency allows girls to carry out sequential movements more quickly and efficiently than boys of the same age, a skill that could be related to any sequential operation from typing to flying a space shuttle.

In tests conducted by Wolff, boys were easily disrupted from keeping time with their fingers when anything interfered with a time-keeping metronome. Girls were not.

While Wolff is cautious, others trace this proficiency to the left half of the brain, which not only controls sequential analysis, but also controls speaking and reading, two skills that girls develop more quickly than boys.

It would be unfortunate, scientists warn, if such experimental knowledge were marshalled to attack or support the women's movement or to suggest that one sex is naturally superior to the other. On the contrary, the evidence suggests a variety of skill-superior ities that cut across the sexes. While girls develop speaking and reading skills faster, boys tend to be more skilled in mechanics and math.

The work of Dr. Deborah Waber at Children's Hospital likewise can be interpreted to show sex differences in brain function, but she, like Wolff, is hesitant to push such a suggestion.

Waber studies "lateralization" in brain function: the amount of sharing of behavioral tasks by the left and right halves of the brain. She has demonstrated that females are less lateralized than males. She has tied this to the well known observation that girls reach puberty sooner than boys. Sexual maturation, it appears, inhibits the brain in sharing functions between the two halves.

Waber's studies have been cited by Dr. Jerre Levy, a neurologist at the University of Chicago, to support Levy's thesis that the sexual hormones - chemicals secreted into the bloodstream by sex glands - make the brains of males and females different.

Levy's theory holds that the right half of the brain is dominant in males while the left half is dominant in females. The sexual hormones appear to be the most important factors in Levy's thesis, but it remains a scientific mystery just where these differences originate.

Levy and other scientists are exploring the possibility that the sex hormones operate in such a way as to "masculinize" or "feminize" a developing brain.

"I think she has gone far beyond what the data reveal," said Waber of Levy's interpretations.

"Hormones and the brain clearly operate in the reproductive function," Waber said. "Everything else is inferential."

Most of the scientific evidence on the role of hormones has been gathered

from experiments on animals, and any conclusions based on studies of humans must remain tentative, warn research endocrinologists Anke Ehrhardt and Heino Meyer-Bahlburg of Columbia Presbyterian Medical Center in New York in a recent Science magazine article summarizing these studies.

In fact, Ehrhardt and Meyer-Bahlburg conclude that experiments studying the effects of sex hormones on general intelligence - that is, total intelligence when all subskills are taken together - produce negative results.

Hormones are tricky. The most glaring example of their effect on humans appears at the beginning of adolescence with puberty. Put simply, the hormones secreted by the gonads are preparing youthful bodies to reproduce.

But the gonads do not lie dormant until adolescence. Some evidence suggests that what happens with the sexual hormones in adulthood is linked to what happens with them when the body and brain are being formed in the earliest stages of development, although the exact connection is not fully understood.

"There are undoubtedly passionate and private motives for wanting to see sex differences in the brain," said Wolff. "We've gone through a long history of environmentalism and now we're seeing the antithesis - everyone is looking for prefixed prenatal determinants."

Waber agrees. "It has an astrological quality," she said. "People are saying to psychologists, Tell me how to read my brain,' as if knowing whether they have a male brain or a female brain is going unlock the key to who they are."

"Most of the sex differences we see in our work are really small differences," Waber said. "Occasionally a glich of difference shows up, but we're talking about brains that still function in pretty much the same way.

According to Dr. Richard M. Restak, a Georgetown University neurologist whose 1979 book, "The Brain: The Last Frontier," summarizes most research on the brain, the question raised from these studies is not "Are there brain-sex differences?" but rather, "What is going to be our response to these differences?"

Research on differences in brain function between the sexes is largely statistical, Restak notes. As such, it uncovers trends and should not be

applied to individuals.

Sigmund Freud claimed anatomy is destiny, but he had neither the scientific knowledge nor the technological tools early in this century to suggest that his poetic dictum was embedded in the anatomy of the human brain.

And whatever the dictum, contemporary researchers cautiously warn, there is no evidence to suggest that destiny implies inferiority or superiority of one gender in relation to the other.