Even among studies that do include both sexes, too many fail to report data by sex, leading to a file-drawer problem. Such omissions are possibly more common when there is no significant difference between sexes, because scientists and

editors are generally uninterested in negative findings. INCB018424 clinical trial But such omissions distort the published literature and lead to biased reviews and meta-analyses. Although it is difficult to publish a negative result, researchers need not dedicate an entire paper to it; a single sentence or brief paragraph in the Results section of their primary study can suffice to make quantitative data about sex differences or similarities publicly available. With regard to human research in particular, new insight may come from studies that are beginning to analyze participants by psychological gender role identity, as opposed to just biological sex.

For example, Paclitaxel nmr Bourne and Maxwell (2010) found that for both males and females, participants’ self-assessed “masculinity” added considerable predictive power to the relationship between emotion perception and functional brain lateralization. A handful of other behavioral and imaging studies have similarly found that a continuous variable akin to “gender”—that is, relative masculinity or femininity assessed using the Bem Sex Role Inventory—maps more closely to brain and psychological function than the dichotomous variable “sex.” Because gender role identity is likely more influenced by life experience than biological sex, such findings may help identify particular types of education, practice, and training that contribute

to average male-female differences in both the brain and behavior. Despite the complexity, neuroscientists can and must persevere in studying sex differences, especially considering males’ and females’ different vulnerabilities to many developmental and psychiatric disorders. Done correctly, research on sex difference provides a fascinating window into the nature-nurture interaction that fuels all of brain and behavioral development. Done incorrectly—that is, without consideration of both social and genetic/hormonal influences much and without attention to the careless extrapolations in public discourse—this science can reinforce some of the worst biological essentialism. I thank William Frost for helpful comments on the manuscript and Larry Cahill, Janet Hyde, Melissa Hines, and M.J. Wraga for valuable discussion at the 2011 Society for Neuroscience Social Issues Roundtable on this topic. Due to format constraints, I was unable to cite a large number of studies that support these views, but I will gladly provide them upon request. “
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