JOHN DARLEY, professor of psychology and public affairs emeritus, died Aug. 31 in Lawrenceville, N.J. He was 80. Darley joined the faculty in 1968, served as chair of the psychology department from 1980 to 1985, and became emeritus in 2013. He popularized the concept of the “bystander effect” following the 1964 murder of Kitty Genovese in New York City and widely publicized accounts of neighbors ignoring the victim’s calls for help. At Princeton, Darley built the social psychology program into a leader in the country and published on altruism and bystander intervention, deviance and conformity, and attribution theory.