Millet, K., & Dewitte, S. (2007, July). Digit ratio (2D:4D) moderates the impact of an aggressive music video on aggression. Personality and Individual Differences, 43(2), 289-294. Retrieved June 27, 2009, doi:10.1016/j.paid.2006.11.024

Digit ratio (2D:4D) is a sexually dimorphic trait. Men have relatively shorter index fingers (2D) compared to ring fingers (4D) than women. Evidence suggests that more masculine ratios are influenced by higher prenatal testosterone levels. Testosterone and aggression are related and accordingly evidence suggests that male 2D:4D is related to physical aggression [Bailey and Hurd, 2005] and female 2D:4D is related to reactive aggression [Benderlioglu and Nelson, 2004]. As it has been shown that violent media have an impact on aggressive behavior, we predict that the relationship between 2D:4D and aggression should be stronger when exposed to an aggressive than to a non-aggressive music video. Accordingly, we show that 2D:4D and aggression (as measured by two different measures) are related, but only after exposure to the aggressive video. We suggest that future 2D:4D research should focus on plausible interactions between 2D:4D and context cues rather than on linear relations. (PsycINFO Database Record (c) 2008 APA, all rights reserved)(from the journal abstract)