Louis Proyect wrote
In Steven Johnson's review of Steven Pinker's "The Blank Slate", we
discover that E.O. Wilson, Stephen Pinker and Richard Dawkins were right
all along. Biology is destiny. Women's brains differ from men's, hence
accounting possibly for men's superiority in theoretical physics among
other things. (Don't worry, gals, your brains might just as easily
prepare you for "social interactions" and "empathy".)
REPLY: I have no idea what Steven Johnson says in the Nation, but we both know
perfectly well that Wilson, Dawkins, and Pinker never argue anywhere that
"biology is destiny".
By coincidence I happened to be reading this apt comment from
Geoffrey Miller quoted in Pinker's "The Blank Slate"
"Viewed sociologically, turning books into ideological touchstones can be
useful. People can efficiently sort themselves out into like-minded cliques
without bothering to read or think. However, there can be more to human
discourse than ideological self-advertisement."
Women's brains do indeed differ from men's, and this does seem to be relevant
where mathematical ability is concerned - see:
Gur, R. C., Turetsky, B. I., Matsui, M., Yan, M., Bilker, W., Hughett, P., &
Gur, R. E. (1999). Sex differences in brain gray and white matter in healthy
young adults: correlations with cognitive performance. Journal of Neuroscience,
Sex Differences Found In Proportions Of Gray And White Matter In The Brain:
Links To Differences In Cognitive Performance Seen
"Head size correlates statistically with intelligence, a not-widely known
fact-greater cranial volumes are linked to higher intelligence. The
while small, has been reported in multiple studies. And because, on average,
men's bodies are bigger than women's, their heads too are larger than women's.
So, one might reasonably expect men to be more intelligent than women. This is
not the case, however - men and women consistently score equally on
intelligence tests. For neuroscientists, this paradox has long presented a
puzzle. If head size correlates with intelligence, and women have smaller
heads, why don't they have lower intelligence?
Researchers at the University of Pennsylvania Medical Center now report new
findings that may help explain the conundrum: Women have a higher proportion of
gray matter to cranial volume than men. Conversely, men have higher proportions
of white matter and cerebrospinal fluid to cranial volume than women. Gray
matter refers to the neuronal cell bodies and their dendrites, the short
protrusions that communicate with immediately neighboring neurons in the brain.
White matter refers to the longer axons, sheathed in a white fat called myelin,
that reach out from neurons to more distant regions of the brain. Cerebrospinal
fluid is the liquid in which the brain floats inside the head. Gray matter is
where computation takes place, while white matter is responsible for
communication between groups of cells in different areas of the brain.
"With these findings, we are beginning to get an explanation for the lack of
intelligence disparity between men and women," says Ruben C. Gur, Ph.D.,
professor of psychology in psychiatry and lead author on the new study, which
will appear in the May 15 issue of the Journal of Neuroscience. "Women have a
higher percentage of tissue devoted to computation than men. Men have a greater
proportion of tissue assigned to the transfer of information between distant
The study replicated the findings associating better cognitive performance with
larger volumes of brain tissue. The researchers determined, however, that with
similar increases in volume, women gain more intelligence than men.
"Women's brains appear to be more efficient than men's in the sense that an
equal increase in volume produces a larger increase in processing capacity in
women than in men," notes Raquel E. Gur, M.D., Ph.D., professor of psychiatry
and neurology and senior author on the study.
The study also offers a possible explanation for long-observed ability
differences between men and women on specific types of cognitive tasks.
Generally, women excel on verbal tasks, while men do better on spatial tasks.
In the current study, these task-specific differences in ability were
reconfirmed and correlated with the newly found proportional differences in
gray and white matter in men and women. While higher volume of tissue
correlated with better performance on both verbal and spatial intelligence
tasks, the highest levels of spatial task performance required greater amounts
of white matter than can be accommodated in the crania of most women.
"When we looked at the top performers for spatial tasks in our study - those
performing better than one standard deviation above the average - there were
nine men and only one woman," Ruben Gur says. "Of these nine men, seven had
greater white-matter volumes than any of the women in the study. This suggests
that, in order to be a super performer in that area, one needs more white
matter than exists in most female brains."
The new data shed light on earlier observations concerning the corpus callosum,
a large body of nerve fibers that connects the right and left hemispheres of
the brain. Those studies showed that women have a relatively larger corpus
callosum than men. The corpus callosum, however, is composed of white matter,
the tissue type seen in this study at lower overall proportions in women than
men in the brain, suggesting that evolution has placed a priority on this
structure in women.
"The implication of women having more white matter connecting between the
hemispheres of the brain is that they would have better communication between
the different modes of perceiving and relating to the world," says Raquel Gur.
"On the other hand, men would demonstrate a stronger concentration on working
within any one of those modes."
Forty men and forty women, all healthy adults, volunteered to participate in
the study. Gray and white matter percentages and overall cranial volumes were
assessed using three-dimensional MRI imaging techniques. Cognitive performance
was measured using tasks designed to examine different types of intellectual
ability. An example of a spatial task given to the study participants involved
viewing an array of lines fanning out at angles. Shown a second set of two
shorter lines at similar angles, the participants were asked to identify which
lines in the original fan array matched the angles of the shorter lines. One
verbal intelligence task involved extrapolations of word relationships. Some
examples: "sailor is to navy as soldier is to: a) gun, b) cap, c) hill, d)
army" and "thoughts are to brains as steam is to: a) water, b) vapor, c)
boiling, d) heat."
In addition to Ruben and Raquel Gur, the coauthors on the study were Bruce I.
Turetsky, Mie Matsui, Michelle Yan, Warren Bilker, and Paul Hughett. Funding
for the research was provided by the National Institutes of Health.
The University of Pennsylvania Medical Center's sponsored research and training
ranks second in the United States based on grant support from the National
Institutes of Health, the primary funder of biomedical research and training in
the nation -- $201 million in federal fiscal year 1998. In addition, the
institution continued to maintain the largest absolute growth in funding for
research and training among all 125 medical schools in the country since 1991.
News releases from the University of Pennsylvania Medical Center are available
to reporters by direct e-mail, fax, or U.S. mail, upon request."
As that notorious biological determinist Stephen Jay Gould recently noted, the
idea of differential parental investment "makes Darwinian sense and probably
does underlie some different, and broadly general, emotional propensities of
human males and females".
Marek Kohn observed
"In one sentence, Gould endorses the basic theoretical foundation of the school
he is excoriating. He accepts the central insight of evolutionary psychology,
and agrees that men's and women's psyches have been shaped differently by
evolution. The only question is that of degree. It is like reading a pamphlet
from the Adam Smith Institute and coming across the observation that "the
history of all hitherto existing society is probably the history of class
struggle". see http://human-nature.com/nibbs/02/kohn.html
Ian Pitchford PhD CBiol MIBiol
The Human Nature Review
Department of Psychiatry
Creighton University School of Medicine
3528 Dodge Street
Omaha, NE 68131, USA