Jerome Kagan in Salon:
Despite many victories, a number of important problems that are amenable to inquiry or reconceptualization are being ignored. First, scientists studying psychological phenomena should replace their habit of linking one cause to one outcome with an examination of the relations between patterns of causal conditions and patterns of outcomes. A single condition (whether a gene, a secure attachment, premature birth, abuse, harsh socialization, or bullying) that ignores the child’s gender, temperament, ethnicity, social class, and culture usually explains little of the variation in most psychological outcomes.
…Steven Pinker’s decision in “The Better Angels of Our Nature” to pool different types of violent actions by agents who varied in gender, age, ethnicity, and motive into a single category called violence is analogous to grouping the olfactory signals of ants, dances of bees, songs of birds, croaks of frogs, grimaces of monkeys, screams of infants, lullabies by mothers, lectures by professors, and spam messages over the Internet into an omnibus category called communication. The probability of a violent act is palpably higher for males compared with females across the life span. Males between seventeen and thirty years of age commit the vast majority of violent behaviors, in the past as well as today. Older men and children are unlikely to kill, rape, or torture anyone. Males between age seventeen and thirty represented a large proportion of the European population between 1200 and 1700 because more than 50 percent of children died before age five and more than 80 percent of adults died before age fifty. By contrast, males between seventeen and thirty make up less than 20 percent of today’s European population. Hence, a scientist who bases the prevalence of violence on the ratio of the number of homicides over the total population would be likely to discover that the rate of violence decreased across the interval from 1200 to 2000 because the proportion of the total population that was male and between age seventeen and thirty had declined precipitously over those eight hundred years.