Schizotypy and altered digit ratios: a second look.

Alterations in the ratio between the 2nd and 4th finger digits have been posited as a potential indicator of increased liability for neurodevelopmental disorders such as autism and schizophrenia. We compared digit ratios in two groups of psychometrically-identified schizotypes, namely, those characterized by positive schizotypy (perceptual aberrations and magical ideation; n=76) and those characterized by negative schizotypy (social anhedonia; n=64), to a control group (n=110). The groups were also compared in terms of their performance on a measure of Theory of Mind, namely, the Reading the Mind in the Eyes Test (RMET) and trait affect, as measured by the PANAS. Our results indicate that neither negative schizotypy nor positive schizotypy is associated with altered digit ratios. Similarly, the groups showed no significant differences on the RMET. However, we observed a small but significant inverse association between Theory of Mind performance and negative affect. The findings are considered in light of the extant literature. These results call into question the viability of altered digit ratios to serve as an indicator of increased risk for schizophrenia-spectrum disorders.