Ratio or Length?
A Proposed Methodology for Understanding Digit Ratio and Personality Using a Female Sample
Abstract
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.
References
(2002). A preliminary investigation of the association between personality, cognitive ability and digit ratio. Personality and Individual Differences, 33, 1115–1124.
(2005). Finger length ratio (2D:4D) correlates with physical aggression in men but not in women. Biological Psychology, 68, 215–222.
(2002). Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia. Hormones and Behavior, 42, 380–386.
(1992). The aggression questionnaire. Journal of Personality and Social Psychology, 63, 452–459.
(2006). Height in women predicts maternal tendencies and career orientation. Personality and Individual Differences, 40, 17–25.
(1985). Personality and individual differences: A natural science approach. New York: Plenum.
(1991). Manual of the Eysenck Personality Scales (EPS Adult). London: Hodder and Stoughton.
(2004). Second to fourth digit ratio and the “big five” personality factors. Personality and Individual Differences, 37, 495–503.
(2007). The 2nd to 4th digit ratio and developmental psychopathology in school-aged children. Personality and Individual Differences, 42, 369–379.
(2001). Understanding internal consistency reliability estimates: A conceptual primer on coefficient α. Measurement and Evaluation in Counseling and Development, 34, 177–189.
(2006). Digit ratio (2D4D) and physical fitness in males and females: Evidence for effects of prenatal androgens on sexually selected traits. Hormones and Behavior, 49, 545–549.
(2007). Behavioral aggression is associated with the 2D:4D ratio in men but not in women. Journal of Individual Differences, 28, 64–72.
(2006). Finger lengths, 2D:4D ratios, and their relation to gender-related personality traits and the Big Five. Biological Psychology, 71, 116–121.
(2009). Relative finger lengths, sex difference, and psychological traits. Archives of Sexual Behavior, 38, 398–405.
(2002). Digit ratio: A pointer to fertility, behavior and health. New Jersey: Rutgers University Press.
(1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and levels of testosterone, LH and estrogen. Human Reproduction, 13, 3000–3004.
(1997). Personality trait structure as a human universal. American Psychologist, 52, 509–516.
(1992). Personality correlates of physical height. Personality and Individual Differences, 13, 1349–1350.
(2005). Item format and the psychometric properties of the Eysenck Personality Questionnaire. Personality and Individual Differences, 38, 61–69.
(2002). The ratio of second- and fourth-digit lengths and congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Early Human Development, 70, 47–54.
(2002). Finger length and distal finger extent patterns in humans. American Journal of Physical Anthropology, 117, 209–217.
(1952). Relative index finger length as a sex-influenced trait in man. American Journal of Human Genetics, 4, 72–89.
(2008). Factors influencing preferences for height: A replication and extension. Personality and Individual Differences, 45, 395–400.
(1990). On the universality of human nature and the uniqueness of the individual: The role of genetics and adaptation. Journal of Personality, 58, 17–68.
(2004). Androgens and bone. Endocrine Reviews, 25, 389–425.
(2005). Psychobiology of personality (2nd ed., revised & updated). New York: Cambridge University Press.
