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From Scanner to Sound Bite:Issues in Interpreting and Reporting Sex Differences in the Brain


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Fine
Moreover, the psychological implications of significant
differences in the amount of brain activity in particular regions
are ambiguous. ‘‘More’’ activity does not necessarily imply
psychologically ‘‘more’’ or ‘better,’’ or even that that region
is critically involved in that particular task (Poldrack, 2008).
Furthermore, data acquisition in functional magnetic resonance
imaging (fMRI) is slow: At its most sensitive, it averages over a
few seconds the activity of millions of neurons that can fire up
to one hundred impulses a second. (Positron emission tomogra-
phy, PET, is even slower.) This massively limits the interpreta-
tions that can be made about brief psychological events.
Thus it becomes clear that observing, say, significantly
greater female anterior cingulate activity over the time course
of the performance of a complex task is unlikely to indicate
what mental process, if any, differs between males or females,
or in what direction that difference lies. It has been argued that
reverse inferences can be valuable when the underlying pro-
cesses involved in the participants’ task are well known, and
when they are used to generate hypotheses that drive further
experimental work rather than to interpret neuroimaging results
(Poldrack, 2008). However, so far these conditions are rarely, if
ever, met in neuroimaging studies of sex differences. These
obstacles to valid reverse inference severely constrain the pos-
sibilities for making inferences about psychological differences
between males and females from brain activation differences,
even supposing these differences reported in studies are statis-
tically valid and reliable.
(as much as 25%) larger in females, furnishing them not just
with superior language skills but also greater multitasking abil-
ity, a more intuitive leadership style, better emotion processing,
and even greater capacity to remember to buy milk (see Fine,
2010).
Even books written by apparently authoritative and well-
credentialed authors are rife with invalid structure–function
claims and reverse inferences, as well as factual errors, that
go well beyond the GML hypothesis. To cite just a few exam-
ples from a multitude, functional neuroimaging findings may
be used as evidence of sex differences in intrinsic interest in
mathematics, in ‘‘hard-wired’’ ability to talk about feelings,
or in capacity to empathize with the feelings of others. As
I have discussed elsewhere (Fine, 2010), these particular claims
were made in part on the basis of studies that, respectively,
didn’t involve mathematics, didn’t involve talking about feel-
ings, and didn’t involve male participants. Furthermore, it
should by now be clear that currently no neuroimaging data
could be cited as compelling support for such claims.
Popular Digestion
In addition to overinterpretation, misinterpretation, and misrep-
resentation, a number of characteristics of neuroscientific
information and the way it is often communicated may further
contribute to public misunderstanding. With its expensive,
complex machinery, the data yielded by neuroscience may
seem somehow more scientific and real than data collected in
less high-tech fashion. A consequence of this ‘‘neuro-realism’’
(Racine, Bar-Ilan, & Illes, 2005) is that substantial behavioral
evidence of gender similarity may be overshadowed by a single
finding of a sex difference in the brain. There may also be a ten-
dency to equate ‘‘in the brain’’ with ‘‘innate.’’ Although the
effects of gender socialization must manifest in the brain
(where else?), some popular authors promote the idea that brain
differences constitute evidence that the sexes are ‘‘hard-wired’’
to be different. Lastly, neuroscientific data have been shown to
have a ‘‘seductive allure’’: For instance, people find circular
explanations of psychological phenomena more satisfying
when accompanied by information about brain responses
(Weisberg, Keil, Goodstein, Rawson, & Gray, 2008). Thus,
popular neuroscience is well placed to entice people to over-
look psychological and sociological data showing that gender
difference is contingent on historical period, ethnicity, socio-
economic group, and social context and to instead conclude
that gender differences are immutable, inevitable, and the prod-
uct of fixed differences between the ‘‘male brain’’ and the
‘‘female brain.’’
Popular Dissemination
While neuroscientists may routinely test for sex differences in
the brain and emphasize those they find, or engage in post hoc
speculations about such differences’ functional implications,
they are presumably aware of the issues outlined previously
and are engaging with peers who share this knowledge. The
public, however, rarely gain its knowledge from neuroscientists
or the neuroscientific literature. Instead, information is pre-
sented to the public by popular writers. That such writers are
either not aware of the critical issues of production and inter-
pretation I have outlined or think them unimportant may be
inferred from the fact that their books confidently purport to
offer practical applications for life, love, and learning on the
basis of sex differences in the brain.
Consider, for example, how the GML is presented in the
popular literature. It is not only regularly asserted as fact rather
than a hypothesis (a poorly supported one, as noted) but is used
as a springboard for scientifically unwarranted claims about
men’s and women’s different psychological abilities. Thus one
author (working from an implicit metaphor of the brain as pin-
ball machine) explains how men’s language lateralization
impairs their ability to talk about their feelings, describing how
the ‘‘signal’’ of an emotional feeling, having made it to the
right hemisphere, ‘‘may well get stopped, disappearing into
neural oblivion because the signal found no access to a receptor
in a language center in the left side of the brain’’ (Gurian, 2004,
p. 88). Similarly, the corpus callosum is regularly claimed to be
Conclusion
While neuroimaging has potential to contribute in novel ways
to our understanding of gender, scientists, popular commenta-
tors, and the public need to be alert to the problem of premature
speculation about sex differences. The possibility of
neuroimaging ‘‘facts’’ about male and female brains—that may
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