Can Sex Differences in Science Be Tied to the Long Reach of Prenatal Hormones? Brain Organization Theory, Digit Ratio (2D/4D), and Sex Differences in Preferences and Cognition

Abstract

Brain organization theory posits a cascade of physiological and behavioral changes initiated and shaped by prenatal hormones. Recently, this theory has been associated with outcomes including gendered toy preference, 2D/4D digit ratio, personality characteristics, sexual orientation, and cognitive profile (spatial, verbal, and mathematical abilities). We examine the evidence for this claim, focusing on 2D/4D and its putative role as a biomarker for organizational features that influence cognitive abilities/interests predisposing males toward mathematically and spatially intensive careers. Although massive support exists for early brain organization theory overall, there are myriad inconsistencies, alternative explanations, and outright contradictions that must be addressed while still taking the entire theory into account. Like a fractal within the larger theory, the 2D/4D hypothesis mirrors this overall support on a smaller scale while likewise suffering from inconsistencies (positive, negative, and sex-dependent correlations), alternative explanations (2D/ 4D related to spatial preferences rather than abilities per se), and contradictions (feminine 2D/4D in men associated with higher spatial ability). Using the debate over brain organization theory as the theoretical stage, we focus on 2D/4D evidence as an increasingly important player on this stage, a demonstrative case in point of the evidential complexities of the broader debate, and an increasingly important topic in its own right. Keywords sex/gender; cognitionWomen's growth in the scientific workforce has been meteoric over the past 40 years (Ceci & Williams, 2010a, 2010b. For example, in 1970, fewer than 5% of scientific and medical doctorates were awarded to women, but by 2006 approximately 50% of MDs and 48-51% of PhDs in biology were being awarded to women, as were 76% of doctorates in veterinary medicine, and 67% of PhDs in psychology.However, there is one glaring exception to women's progress in scientific careers. In fields that are highly quantitative, women's success has been far less pronounced. In 2006, less than a third of the PhDs in highly quantitative fields were awarded to women: 29.6% in mathematics, 21.3% in computer science, 29% in physical sciences, and 20.2% in engineering (Burrelli, 2008, Table 1). In the top 100 US universities, only 8.8% (in mechanical engineering) to 15.8% (in astronomy) of all professorial ranks combined in many quantitative fields are occupied by women (Nelson & Brammer, 2010, Table 11). © The Authors(s) 2011Corresponding Author: Jeffrey Valla, Department of Human Development, Cornell University, G79, MVR Hall, Ithaca, NY 14853, jmv34@cornell.edu. NIH Public Access Author ManuscriptPerspect Psychol Sci. Author manuscript; available in PMC 2011 December 5. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptAmong full professors, women usually number less than 10% in the following fields: chemistry, 9.7%; mathematics, 7.1%; computer science, 10.3%; physics, 6.1%; chemical engineerin...

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