ABSTRACT
Coevolution of instincts of aggression and escape may have ensured that expression of the former (threatening vocalisation) serves as the key to the latter (fearful reaction) in another individual. Group behaviour is determined, from a drive-motivational point of view, by successive impulses of "aggression, fear, protection-seeking and renewed aggressiveness". Appetitive behaviour for fighting points to the existence of an innate drive for aggression. The drive for aggression is aroused not only by frustration but also by pain—occasionally to the point that aggressive motor patters are expressed spontaneously, that is, in the absence of a suitable releasing "stimulus situation". The evolution of intraspecific aggression necessitated that "the effectiveness of the original motor patterns should be considerably reduced and with it the danger of physical injury to the combatants". Unlike defensive aggression, offensive aggression usually ensues after complex "affective cost-benefit analysis".
