Musafer Sherif, 82, who became a social psychologist while an economics student at Harvard University because the 1929 stock market crash showed him "there was something very wrong" with the United States, his adopted homeland. Sherif, a native of Turkey, became known for his so-called "Robber's Cave" experiment in which two groups of 11 boys each were alternately teamed in work projects and then pitted against each other in competitions. The experiment, named after the summer camp where it was conducted, became the subject of a 1961 book by Sherif and has become a leading example of how people can learn to cooperate, to battle and then to cooperate again. Sherif, who wrote several books on social psychology, taught or did research at Princeton and Yale universities and most recently at the University of Pennsylvania where he retired in 1972. In Fairbanks, Alaska on Oct. 16 of a heart attack.