Testosterone and aggression: A reanalysis of Book, Starzyk, and Quinsey's (2001) study

A critique is presented of the meta-analysis of testosterone and aggression by Book, Starzyk, and Quinsey [Aggression and Violent Behaviour 6 (2001) 579], and the results of a reanalysis of their data are reported. We identified the following problems with their analysis: Secondary, rather than primary, sources were used in the initial literature review; 15 studies were included that should have been omitted; there were no decision rules for calculating effect sizes, leading to inaccuracies in most of these; the statistical test used to compare categories was of low power; the coding of study characteristics was inaccurate. A reanalysis that corrected these problems produced a lower mean weighted correlation (r=.08 instead of the reported r=.14). The conclusions from our categorical comparisons were different from those of Book et al.: Neither of their positive findings (a decline with age; lower correlations in morning than afternoon samples) were confirmed. We found significant differences for sex, age, offender status, and source of hormone measure, all of which are different from those in the original analysis.