The claimed link between dominance and free testosterone is an intriguing one but problems remain in attempting to link this single hormonal measure to human behaviour. These include the heterogeneous nature of dominance, the precise nature of the correlation(s), and whether only testosterone is important.

A test of a biosocial model is reported in which we found no impact of circulating testosterone on either status-seeking or aggression. The fact that sex differences in competitiveness and aggression appear in childhood strongly suggests that the major impact of testosterone is organisational. Whereas dominance and resources are linked among males, female aggression may be a function of pure resource competition, with no element of status-seeking.

The testosterone–dominance model is noteworthy but should incorporate the ecological factors that often underlie variability in basal testosterone. This is evident in the ethnic testosterone differences discussed in the target article (sect. 8). The significance of acute changes in testosterone levels in response to competition is also poorly understood. Significant metabolic effects have been reported, suggesting that other physiological explanations should be explored, independent of potential behavioral or social factors.

There is evidence that in women high levels of testosterone are associated with more sexual partners and more permissive sexual attitudes. If a similar relationship holds true for men, the higher basal testosterone levels of divorced and unmarried men may be caused by this relationship rather than by testosterone's effect on dominance striving.

The following three points are made. One must consider not only the levels of circulating hormone but the target tissue upon which the hormone acts. Increased testosterone levels alone do not account for differences in displayed intermale aggression, because testosterone and social environment interact in complex ways to influence behavior. A given behavior can be triggered by multiple motivational systems.

The basal and reciprocal models of the relationship between androgen secretion and dominance are not mutually exclusive. Individuals may differ in basal levels of androgen secretion, reactivity to experiences, and androgen sensitivity. Early experiences might affect any of these parameters.

Culture and social structure may affect the testosterone–behavior link by shaping the way we construe events; by muting, channelling, or amplifying the drives that testosterone produces; and by affecting the distribution and level of testosterone in various parts of the population. Research on testosterone, culture, and social class has produced suggestive results, opening broad areas for research.

Mazur & Booth's target article presents strong evidence that social factors influence testosterone; however, the evidence for an effect of testosterone on dominance is considerably weaker. Although social and biological factors may interact, as suggested in the reciprocal model, findings in rhesus monkeys suggest that social factors may predominate. Finally, research is needed to evaluate whether androgens during early life influence later dominance.

Studies of testosterone's effect on dominance are confounded by the effects of dominance experiences on testosterone. Furthermore, antisocial behavior tends to originate prepubertally, when testosterone levels are the same for aggressive males, nonaggressive males, and females. It seems more parsimonious to view variation in testosterone as an effect of dominance-related mood states than to invoke a reciprocal model.

Prenatal exposure to high levels of testosterone may lead to increased probability of left-handedness. Extrapolating from arguments by Mazur & Booth leads to a prediction of increased incidence of antisocial behavior among left-handers. Six hundred ninety-four males were tested for seven indicators of delinquency in high school. Left-handers were more likely to display such behaviors, providing indirect evidence for the hypothesized behavioral effects of testosterone.

In the animal literature, the concept of dominance usually links status in intermale encounters with differential reproductive success. Mazur & Booth effectively review the human literature correlating testosterone with intermale competition, but more profound questions relating this to male–female dynamics have yet to be addressed in research with humans.

Testosterone is related to dominance, but in a broader sense than Mazur & Booth suggest. Dominance need not be competitive. It can arise from strong personal characteristics that produce admiration and deference in others. To understand the testosterone–dominance relationship fully, we must examine behaviors that affect ordinary social encounters. Baseline testosterone levels may be more important than testosterone changes in predicting everyday dominance.

Mazur & Booth have shown an association between testosterone and dominance behavior, but the strength of the relationship is not given. In addition to being statistically significant, it is also necessary that testosterone account for a meaningful proportion of the variance; a multivariate model is probably necessary. A cautionary tale from the animal literature is related.

The human neuroendocrine system is highly sensitive to the social environment. Hormones such as testosterone and cortisol are released in response to a wide variety of social stimuli. The evolutionary functions of this sensitivity are not well understood. Longitudinal monitoring of hormones, behavior, and social environment is a promising research paradigm for solving these evolutionary puzzles.

Because the reciprocal theory of Mazur & Booth dominates the static basal model, given the evidence they present, it is worth considering the implications for women's equality, supposing it true. Testosterone might well give males a competitive edge, and hence higher status, creating an inequality that mere social legislation would be ill-suited to address. Further research on the role of testosterone is needed.

Using testosterone alone as a measure of dominance presents problems, especially when dominance is loosely defined to include a range of behaviors that may arise from multiple causes. Testosterone should be examined in relation to other hormonal and neurotransmitter factors, such as serotonin. Various hypotheses about the relationship between high and low levels of testosterone with serotonin and with impulse control are suggested for future study.

Seen in its historical context, Mazur & Booth's (M&B's) target article may come to be viewed as a turning point in the study of the biological basis of human behavior in general, and dominance in particular. To facilitate further research, suggestions are offered for making the definition of dominance more precise. From an evolutionary point of view, the testosterone-dominance link may be as important in women as it is in men.

Our commentary summarises the current understanding of how testosterone can be used as a mechanism to link quality to external traits potentially used in sexual signalling, particularly female choice. Testosterone-dependent traits may reveal male's status to rivals and immunocompetence to females. We highlight some interesting unanswered questions and suggest that cross-disciplinary collaboration would help solve them.

There is substantial evidence that psychological factors influence human testosterone levels, but little support if any for an influence of circulating testosterone on dominance in men. Persistent interest in testosterone as an explanation of behaviors such as dominance and aggression might reflect the influence of cognitive schemas regarding race and sex rather than empirical evidence.

(1) Mazur & Booth do not explain precontest rise in testosterone. Anticipatory T rise may result from fantasized dominance scenarios. (2) Mazur & Booth conclude that females do not experience the dominance–T rise effect. The data are insufficient for this judgment. (3) Mazur & Booth misstate my position on T and sexuality. I offer an emendation and correction.