Male chimpanzees are about twenty times as likely to fight as females are, but the fights don’t last more than a few minutes and rarely result in major injury. Two male chimps who fight each other this morning may be grooming each other this afternoon. According to Frans de Waal, a primatologist at the Yerkes National Primate Research Center in Atlanta, “Picking a fight can actually be a way for [male chimps] to relate to one another, check each other out, and take a first step toward friendship.” Female chimps rarely fight, but when they do, their friendship is over. The hostility that results can last for years. Serious injury is also more likely to occur when female chimpanzees fight. Female chimps who have fought each other are “vindictive and irreconcilable, according to Dr. de Waal.
In our species these differences are apparent as soon as children can talk. Boys as young as two years of age, given a choice between violent fairy tales and warm and fuzzy fairy tales, usually choose the violent stories. Girls as young as two years of age most often choose the warm and fuzzy stories. In another study psychologists found that five- and seven-year-old girls who like to make up violent stories are more likely to have significant behavior problems than girls who prefer warm, nurturing stories. However, among boys, a preference for making up violent stories is not an indicator of underlying psychiatric problems. A preference for violent stories seems to be normal for five- to seven-year-old boys, while the same preference in five- to seven-year-old girls suggests a psychiatric disorder.
Leonard Sax – Why Gender Matters p.51