Haier, Jung, Yeo, Head, and Alkire (2005) found that men have more gray matter (neurons, synapses, see more dendrites) in fronto-parietal brain regions whereas women have more white matter (myelinated axons). Moreover, in males, intelligence is correlated more with gray matter areas whereas in females white matter areas are correlated higher with intelligence (for a review cf. Deary, Penke, & Johnson, 2010). Remarkably, during explicit
stereotype exposure the neural efficiency phenomenon could no longer be observed, neither for boys nor girls. In this condition boys received the message that they usually perform better than girls. Boys might have reframed this stereotype as a challenge. Considering a test situation as a challenge is known to lead to increased performance (Alter et al., 2010 and Keller, 2007). The arousal associated with this challenge could also result in increased brain activation, especially in high IQ boys who typically ERK inhibitor show lower brain activation (Neubauer & Fink, 2009). This might explain why no neural efficiency was observed in this
specific task condition. In a similar vein, the reported brain activation pattern found for girls in the stereotype exposure condition might also be the consequence of the increased performance pressure. However, in contrast to boys the stereotypic expectancies for girls result in a threat experience, because of the possibility to confirm the stereotype. This argument appears to be supported by the finding that the stereotype exposure condition was associated with higher arousal in terms of higher TRP. Moreover, the selective increases in brain activation due to increased arousal could again have counteracted the general phenomenon of neural efficiency. Our results provide preliminary evidence that the stereotype threat itself cannot explain sex differences in neural efficiency in visuo-spatial tasks. Results corroborate the neural efficiency hypothesis for men only when
sex differences were described to be irrelevant. This suggests that for visuo-spatial sex differences in brain activation patterns may be caused by biological but also by long term social factors like learned or socially determined interests and not only short-lived stressing effects of stereotype threat on performance. It still has to be acknowledged that activated stereotypes significantly affected brain activation, but they are probably not responsible for the reported sex differences in neural efficiency during visuo-spatial tasks. Therefore, it is still important to consider the phenomenon of stereotype threat in forthcoming studies. A replication of the present findings including a verbal task could be of particular interest for future investigations, as this would represent a stereotype threat for boys and a stereotype lift for girls.