Testosterone and aggression: A reanalysis of Book, Starzyk, and Quinsey's (2001) study
Introduction
Book, Starzyk, and Quinsey (2001) undertook a meta-analysis of studies linking testosterone and aggression. While such quantitative syntheses are important for advancing knowledge in a particular area and are generally preferable to qualitative reviews Cooper, 1984, Schmidt, 1992, there are certain problems with undertaking a meta-analytic review that these authors appear not to have addressed. As a consequence, some of their conclusions are likely to be unsound. In this commentary, we outline these problems under the following headings: (1) the derivation of hypotheses by qualitative reviews of secondary rather than primary sources in the background literature; (2) the inclusion of studies that should have been omitted, because they were duplicate entries from the same sample, were not concerned with the association between testosterone and aggression, or did not involve a measure of aggression; (3) ambiguity in the decision rules for calculating effect sizes for the association between testosterone and measures of aggression, leading to inaccuracies in the majority of their effect-size values; (4) statistical problems in comparing categories; (5) inaccuracies in coding the study characteristics, leading to inaccuracies in the categorical analysis.
In addition to outlining these problems, we have examined all studies used by Book et al. (2001) in their analysis, reassessed whether they should be included, recalculated the effect sizes, recoded the categorical variables, and analyzed these values. We then compared the conclusions from this reanalysis with those reached in the original analysis. We conclude that there are sufficient grounds for questioning most of the conclusions in the original analysis. Finally, we make some general observations about the utility of meta-analytic reviews.
Section snippets
Review of the literature
It is important that research questions are accurately identified in the review of previous literature. This requires accurate characterization of what is already established and separating this from widely repeated but erroneous statements found in secondary sources and texts. Book et al. (2001) relied on a few book chapters for most of their background review, leading to the presentation of secondary sources as empirical studies and to some inaccurate characterization of what is established
Which studies should be included in the meta-analysis?
Inspection of Table 1 by Book et al. (2001) indicates several studies that should not have been included in a meta-analysis of the association between testosterone and aggression. There are three reasons why some studies should have been excluded: (1) duplication of the same sample, (2) studies involving the effect of competition on testosterone levels, and (3) studies involving no aggression measures.
We identified two cases of sample duplication. In one, the same sample was entered three
Calculation of effect sizes
Effect sizes listed by Book et al. (2001) were r values for the association between testosterone and measures of aggression. This may appear straightforward, but in many studies, there are multiple measures of testosterone (and other androgen levels), and multiple measures of aggression. Thus, Table 1 of the earlier review by one of the present authors (Archer, 1991) showed several different correlations for each study. Unless clear selection rules are followed, the same data may lead to
Statistical problems in comparing categories
Meta-analysis is as important for identifying comparisons between subgroups as it is for enabling an overall effect size to be calculated. The method adopted by Book et al. (2001) is not entirely clear. It appeared to be a comparison of the numbers of expected and observed correlations in different categories (p. 591), using χ2. It is more usual to compare across different categories using a categorical model test equivalent to a one-way analysis of variance Hedges & Olkin, 1985, Johnson, 1989.
Recoding and reanalysis of study characteristics
Although we have presented a reanalysis of Book et al.'s (2001) comparisons between categories, based on their figures, our discussion in 2 Review of the literature, 3 Which studies should be included in the meta-analysis? showed that both the selection of samples and the effect sizes they used were unsound. We therefore decided to undertake a reanalysis of categorical variables with our revised figures. Although Book et al. provided a table for the reliability of the coded variables, there are
Conclusions
The specific conclusions from our meta-analysis of the studies used by Book et al. (2001) are that their analysis is unsound in several respects: the choice of studies to include, the calculation of study-level effect sizes, and coding of the variables. Each of these has repercussions for the conclusions we can draw from the analysis. Instead of a mean weighted correlation of r=.14, reanalysis produced a considerable smaller value (r=.08), although this was still significantly different from
References (62)
- et al.
The relationship between testosterone and aggression: A meta-analysis
Aggression and Violent Behavior
(2001) - et al.
Testosterone, and winning and losing in human competition
Hormones and Behavior
(1989) A few good men: Evolutionary psychology and female adolescent aggression
Ethology and Sociobiology
(1995)- et al.
Androgen levels and components of aggressive behavior in men
Hormones and Behavior
(1987) - et al.
Testosterone, crime, and misbehavior among 692 male prison inmates
Personality and Individual Differences
(1995) - et al.
Testosterone differences among college fraternities: Well-behaved vs rambunctious
Personality and Individual Differences
(1996) - et al.
Testosterone and personality among college students and military veterans
Personality and Individual Differences
(1990) - et al.
Saliva testosterone and criminal violence among women
Personality and Individual Differences
(1988) - et al.
Disinhibitory sensation seeking, personality and gonadal hormones
Personality and Individual Differences
(1980) - et al.
Sex differences in testosterone response to a video game
Evolution and Human Behavior
(1997)
Salivary testosterone and cortisol in disruptive children: Relationship to aggressive, hyperactive, and internalizing behaviors
Journal of the American Academy of Child and Adolescent Psychiatry
Gender differences in the validity of testosterone measured in saliva by immunoassay
Hormones and Behavior
The influence of testosterone on human aggression
British Journal of Psychology
The association between testosterone and aggression among young men: Empirical findings and a meta-analysis
Aggressive Behavior
Sex hormones in murderers and assaulters
Behavioral Science and the Law
Salivary testosterone and cortisol in a delinquent and violent urban subculture
Journal of Social Psychology
The effects of hormones, Type A behavior pattern, and provocation on aggression in men
Motivation and Emotion
Testosterone and men's marriages
Social Forces
Serum testosterone in violent and nonviolent young offenders
Journal of Clinical Psychology
Hormonal, anthropometrical, and behavioral correlates of physical aggression in !Kung San men of Namibia
Aggressive Behavior
The integrative research review
Saliva testosterone and criminal violence in young adult prison inmates
Psychosomatic Medicine
Age, testosterone, and behavior among female prison inmates
Psychosomatic Medicine
Salivary testosterone and cortisol among late adolescent male offenders
Journal of Abnormal Child Psychology
Homicide
Killing the competition: Female/female and male/male homicide
Human Nature
Evolutionary psychology of male violence
Plasma testosterone: Correlation with aggressive behavior and social dominance in man
Psychosomatic Medicine
Serum cortisol, testosterone, and testosterone-binding globulin responses to competitive fighting in human males
Aggressive Behavior
Aggressive behavioral characteristics, hormones, and sexual orientation in men and women
Aggressive Behavior
Hormonal responses to competition in human males
Aggressive Behavior
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