Abstract: | Two studies were conducted using the Buss aggression machine paradigm to investigate the mediational role of physical exercise with respect to subsequent aggression in relation to the presence or absence of previous instigation. The irritability level of subjects was taken into account in the first study, and the subject' emotional susceptibility level in the second study. In both studies sex differences were also considered so that each study resulted in a 2 × 2 × 2 × 2 design with ten subjects in each cell. As far as irritability is concerned, experimental subjects (pedaling on a bicycle ergonometer) delivered higher shocks than controls (who just waited out the 10 min the experimental subjects were pedaling), independent of irritability level or of the presence or absence of previous instigation. When emotional susceptibility was taken into consideration, physical exercise associated with high level of emotional susceptibility and previous instigation resulted in increased intensity of the shocks subsequently delivered. These findings are discussed in terms of the importance of stable personality characteristics that may differentially mediate aggression. |