Pii: S0191-8869(98)00179-2

Sex di€erences in the Big Five personality structure, as assessed by combined JPI and PRF scales, were examined in a student population (N=528) using factor analytic and covariance structure analysis techniques. An evolutionary hypothesis was tested, that the factor which lies between classical Agreeableness vs. Hostility and Neuroticism vs. Emotional Stability is the basic dimension of dominance-related aggressiveness maintained by frequency-dependent selection. The hypothesis predicts that this factor should explain more variance in males than in females. It was found that females were characterized by higher scores on the factor of Agreeableness and low Emotional Stability vs. Hostility and high Emotional Stability. As predicted, the factor of Agreeableness and low Emotional Stability explained signi®cantly more variance in males than in females, both absolutely and in relation to other personality factors. The between-sex di€erences in personality factors are discussed in relation to studies of temperament, dominance and aggressiveness in non-human animals. # 1999 Elsevier Science Ltd. All rights reserved.