Abstract

Differences between the brains of women and men are often taken as evidence that human brains belong to two types (“female” and “male” brains) or aligned along a male-female continuum (e.g., the extreme male brain theory of autism). Yet, animal studies reveal that sex effects on the brain are exerted by genetic, hormonal and environmental factors that act via multiple independent mechanisms, and are modulated by internal and external conditions. These observations led to the hypothesis that sex effects do not add-up consistently, but rather ‘mix-up’ within each brain to create unique ‘mosaics’ of female-typical and male-typical features. Analysis of magnetic resonance images of human brains and of post-mortem measures of human hypothalamus supported the mosaic hypothesis. A recent analysis of the structure of over 2,100 brains revealed that the brain “types” typical of women are also typical of men, and vice versa, and that large sex/gender differences are found only in the frequency of some rare brain types. This new multi-dimensional description of human brains has implications for scientific efforts to study sex and the brain as well as for social debates on long-standing issues such as the desirability of single-sex education and the meaning of sex/gender as a social category.

Short bio: Daphna Joel is a professor of psychology and neuroscience at Tel-Aviv University. For many years she had studied the involvement of basal ganglia-thalamocortical circuits in normal and abnormal behavior. More recently, Prof. Joel has combined her expertise as a neuroscientist with her interest in gender studies and expanded her work to research questions related to brain, sex and gender. In her research, she uses a wide range of methods to analyze diverse datasets, from large collections of brain scans to information obtained with self-report questionnaires.