Testosterone and aggression

In this chapter we have shown that the role of testosterone in modulation of aggression and related behavior is more complex than the simple cause and effect model originally derived from selective animal studies. A broader evolutionarily-based theory (the “Challenge Hypothesis”) provided the basis for considering research that now dates back over 40 years, ranging from the initial correlational studies, to recent studies that involve sophisticated manipulation of testosterone levels, laboratory procedures rooted in experimental social psychology, and brain imaging. Taken together the emerging evidence shows that competitive behavior influences testosterone levels, which in turn influence aggressive behavior, in a complex way that is moderated by individual differences in personality.