Vol. 4, No. 2, 1998 Page 6


Studies link high levels of the male hormone testosterone to aggression-but elevated testosterone alone doesn't account for aggressive behavior. In fact, successful athletes and businessmen tend to have high testosterone levels, without being any more violence-prone than their low-testosterone counterparts.

Paul C. Bernhardt suggests that testosterone may not act alone in promoting aggression. Rather, he suggests, aggressive men's behavior may be influenced by high testosterone levels combined with low levels of the brain chemical serotonin.

Bernhardt notes that testosterone is linked more strongly to dominance in general than to aggression. But what happens, he asks, when a high-testosterone man is frustrated in his attempts to achieve dominance? Then, Bernhardt speculates, serotonin comes into play, because low serotonin activity is associated with hyperresponsiveness to aversive stimuli.

In short, Bernhardt theorizes, high testosterone levels encourage dominance-seeking behaviors, "which put the individual into situations in which frustration of dominance can occur." When this happens, low serotonin levels result in a greater likelihood of an intensely negative emotional reaction, and, thus, a greater chance of aggressive behavior.

Bernhardt speculates that the hypothalamus and amygdala, "prominently associated with both testosterone and serotonin," play a key role in aggressive responses to situations in which efforts at dominance are frustrated. He notes that "low serotonin levels have been found in the hypothalamus and the amygdala in aggressive animals," and that "testosterone action in both of these brain structures has been shown to increase aggression in various animal species."


"Influences of serotonin and testosterone in aggression and dominance: convergence with social psychology," Paul C. Bernhardt, Current Directions in Psychological Science, Vol. 6, No. 2, April 1997, pp. 44-48. Address: Paul C. Bernhardt, Department of Educational Psychology, MBH 327, University of Utah, Salt Lake City, UT 84112.

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