> There's no strong reason to suggest that this difference is due to anything other than social pressure.

Not entirely true. Differences between male and female behavior and interest can be demonstrated on the first day of life in humans, and can even be demonstrated in other species of animals such as rodents.

> In summary, we have demonstrated that at 1 day old, human neonates demonstrate sexual dimorphism in both social and mechanical perception. Male infants show a stronger interest in mechanical objects, while female infants show a stronger interest in the face. At such an age, these sex differences cannot readily be attributed to postnatal experience, and are instead consistent with a biological cause, most likely neurogenetic and/or neuroendocrine in nature. http://www.math.kth.se/matstat/gru/5b1501/F/sex.pdf

There are physical differences between the structure of male and female brains:

> Using magnetic resonance imaging, we assessed gray matter volumes in several cortical regions in 17 women and 43 men. Women had 23.2% (dorsolateral prefrontal cortex) and 12.8% (superior temporal gyrus) greater gray matter percentages than men in a language-related cortical region, but not in a more visuospatially related cortical region. These data seem to establish sexually dimorphic structural differences in the cerebral cortex, consistent with ptior cerebral blood flow reports. http://www.sciencedirect.com/science/article/pii/09254927950...

> The really significant difference, however, shows up in where language is processed in the male and female brains. The left and right hemispheres of women process language almost equally; while in men, language is processed almost exclusively by the left hemisphere. This symmetrical processing by the female brain is not limited to language applications, and is probably a result of a corpus callosum that is 20% larger in females than in males. (Eliot 1999:380-81,432; Kommer 2006: 248)

> Spatial tasks are among those other applications females process bilaterally. For men, however, spatial tasks are processed in the right hemisphere. (Rilea 2008:2) http://www.erha.org/buettner/spatial.htm

Based on current research it seems premature to conclude that the differences in performance or personal interest are /entirely/ social. Some research on the topic of performance differences between boys and girls:

> More than 50 years of psychological testing and research have yielded the consensus that "the most persistent of individual differences on mutlifactor tests of psychological functioning is a sex difference in spatial ability. Males have decidedly better spatial skill than females" (Harris 1978). In a detailed meta-analysis of the studies of cognitive sex differences, Rosenthal and Rubin (1982) concluded that, although the magnitude of such differences has declined in recent years, sex differences in cognitive functioning are still nontrivial and of real practical importance. The few nonhuman species for which there are comparative data suggest the generality of this phenomenon: among both wild and laboratory rodents males perform significantly better than females on spatial tasks. http://www.jstor.org/discover/10.2307/2461648?uid=3739256...

> For instance, men and women perform comparably on such language skills as verbal reasoning and vocabulary, and men actually outperform women on verbal analogies. Women, despite their supposed mathematical shortcomings, are better at numerical calculations. (Eliot 1999:380, 431)

> Men do perform better on certain spatial tasks; for example, mentally rotating objects in space and reading maps/locating landmarks. Women, researchers have found, are better at remembering the location of objects in a large array. (Eliot 1999: 221; Understanding the Brain 2007:103; Sherry 1997:50)

> A large sex difference in mathematical ability in favor of boys was observed in every talent search. It is notable that we observed sizable sex differences in mathematical reasoning ability in 7th grade students. Until that grade, boys and girls have presumably had essential the same amount of formal training in mathematics. Thus, the sex difference in mathematical reasoning ability we found was observed before girls and boys started to differ significantly in the number and types of mathematics courses taken. http://www.vanderbilt.edu/peabody/smpy/ScienceFactOrArtifact...

> Sizable performance and participation rate differences have existed between male and
female candidates on the College Board Admissions Testing Program's (ATP) Physics Achievement Test for many years (Pfeiffenberger, 1974) http://research.collegeboard.org/sites/default/files/publica... (this report concludes that the performance difference vanishes when comparing boys and girls with many semesters of physics training, but notes that far fewer girls undertake the training than boys).