Critiques and side-notes concerning 2D:4D ratio and prenatal testosterone theory

"Indeed, in carrying out this review we have identified numerous inconsistencies and have raised alternative interpretations of the 2D/4D ratio studies that, taken together, temper claims related to early brain organizational theory. Although nothing in this review refutes this theory, far stronger support for it is needed if it is to account for the dearth of women in mathematical fields. (...) Support for early brain organization theory will require closer interleaving of correlational and experimental evidence. Most of the support for this theory has come from studies that were designed in response to a handful of prior studies—which is how good science accumulates. However, in the case of early brain organization theory, studies are needed that respond to the topography of the theory rather than to one of its high-relief landmarks. Future research will need to be framed in terms of the larger theory instead of local hypotheses. Such an approach will protect against the short-sightedness that sometimes characterizes this literature."

(Valla, Jeffrey M., and Stephen J. Ceci. "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." Perspectives on Psychological Science 6.2 (2011): 134-146.)

"[W]e investigated the relation of 2D:4D with Baron-Cohen’s measures of empathising (“Reading the Mind in the Eyes” test, RMET; Empathy Quotient, EQ), systemising (Systemising Quotient, SQ), and autistic-like traits (Autism-Spectrum Quotient, AQ) in the general population (N = 423 Austrian adults). Whereas sex differences into the expected direction and of expected size were obtained for all variables and internal scale consistencies tallied to retrievable reference values, 2D:4D was unrelated to RMET, EQ, SQ, and AQ scores. Candidate explanations for this lack of correlation might be possible developmental timing differences in the expression of 2D:4D and empathising/systemising, qualitative (as opposed to quantitative) functional differences between the normal and the autistic mind, or the suboptimal psychometric properties of the measures."

(Voracek, Martin, and Stefan G. Dressler. "Lack of correlation between digit ratio (2D: 4D) and Baron-Cohen’s “Reading the Mind in the Eyes” test, empathy, systemising, and autism-spectrum quotients in a general population sample." Personality and Individual Differences 41.8 (2006): 1481-1491.)