Isolation experiments involving X. helleri .male.male. can lead to differing results when achieving aggressive readiness by different methods. Adult X. helleri .male.male. deprived of social experience as they grew up differed in the frequencies of their aggressive and sexual behavior from .male.male. only briefly isolated as adult animals. The Kaspar-Hauser rearing technique was not directly comparable to isolation experiments in involving adult animals. To eliminate possible interaction between agressive and sexual readiness, isolation experiments were conducted using young immature X. helleri and H. burtoni individuals, although these showed some slight sexual behavior. While both aggressive and sexual readiness increased in X. helleri, only the former increased in H. burtoni. The frequency of pairing acts remained unchanged.