While aggression is an identifiable part of the behavioral repertoire of many species, including man, cruelty seems peculiar to the human species. It could, perhaps, be argued that a cat playing with a mouse is enjoying the exercise of power; but it is unlikely that the cat either hates the mouse or is capable of entering into the mouse's presumed feelings of terror and helplessness. Indeed, some authorities would not only deny that predation was cruel in the sense in which we apply the word to human behavior, but would remove it from the category of aggression altogether, confining the use of the word aggression to conflict between conspecifics. Whatever view one takes, there can be no doubt that aggression serves a number of different functions and is essential for survival, while cruelty is not only a blot upon the human escutcheon, but serves no obvious biological purpose. Indeed, one might argue that cruelty is the opposite of adaptive. Edward Wilson has recently contended that reciprocal altruism in human, and to some extent in animal, societies is an adaptive device likely to promote the survival of each participant. 1 In other words, kindness to other human beings is likely to pay in terms of survival and reproductive potential; or as a friend of mine used to put it, “Civility is cheap, but it pays rich dividends.” Human cruelty, therefore, is a phenomenon which is not only repulsive, but requires explanation.
Regrettably, the cruel behavior of human beings is far too common to be explicable solely in terms of psychiatric abnormality, or of special social conditions, important though these are. Violent and cruel behavior is a potential in normal people. But let us look at some of the factors which appear to make cruelty more likely, and begin by considering one kind of abnormal person. In any Western society, there are inevitably a few individuals who lack the normal degree of control over immediate impulse. These are the so-called aggressive psychopaths who commit violent offenses of various kinds, and who may show an almost complete disregard for the feelings of their victims. These are the abnormals whom idealists would like to blame for the whole sum of human cruelty, but who are actually too few in number to make more than a small contribution toward it. We do not understand all the reasons for the psychopath's lack of control of violence. As with other psychiatric conditions, the causes are multiple.
As we know, some suffer from genetic abnormalities; others show what appears to be a delayed maturation of the central nervous system, as evidenced by the persistence, in the electroencephalogram, of electrical