In July 1942 the German army's 101st Battalion, made up mostly of young draftees, was ordered to comb a village near Lublin in search of Jews. Able-bodies men were sent off to labour camps; women, children and the elderly were exterminated. Squads took turns in implementing the carnage over the length of the day: soldiers chose their victims and killed them, one after the other, with a shot in the head. There was a break for lunch, and then the executions continued until evening. This massacre was followed by another twelve; in little more than a year the 101st Battalion murdered at least 38,000 people. How could norms that usually direct people to help and protect their fellow men be so savagely subverted? Psychology's contribution to the study of such dreadful issues has been decisive, yet remains relatively little known. The author shows how "moral exclusion" of the other makes possible cruelty, violence, torture, even extreme cases such as the Shoah and the Cambodian "killing fields".

Marcella Ravenna teaches Social and Group Psychology at the University of Ferrara.