Ratio or Length? A Proposed Methodology for Understanding Digit Ratio and Personality Using a Female Sample

Mounting evidence suggests a link between digit ratio (2D:4D) and personality ' albeit with generally small effect sizes.While the identified effects are usually attributed to in utero biochemistry, the bivariate approach favored by researchers in this area does not rule out competing explanations. After first scrutinizing the independence of 2D:4D and overall finger length, we used a multivariate approach to predict the three-dimensional EPQ-R. Given that ring finger length and digit ratio varied conjointly, we introduced a logarithm of residuals model. This new method simultaneously addresses (1) the sensitivity of 2D:4D to measurement error and (2) the high correlations between 2D:4D and finger length. The traditional 2D:4D measure predicted neuroticism but not psychoticism. The logarithm of residuals model was able to identify specific personality effects for ring and index finger residuals.Both neuroticism and psychoticism were related to finger residual measures in a manner consistent with Manning's in utero biochemistry theory.