Leon Festinger, 69; Influential Theorist in Social Psychology

Psychologist Leon Festinger, who during a 47-year career as a teacher and writer developed the theory of cognitive dissonance to help explain seemingly irrational human behavior, died Saturday of liver cancer. He was 69.

Festinger, a New York City native, was professor of psychology at the New School for Social Research from 1968 until his death. He died at his New York home, the New School said.

“He certainly was one of the most influential psychologists of our time,” said Robert Johnson, professor of social psychology at Columbia University.

Festinger wrote dozens of articles and books on psychology, including several on the theory of cognitive dissonance, which occurs when two simultaneously held thoughts, opinions or beliefs are inconsistent.

A City College of New York graduate, Festinger went on to get his master’s and doctorate from Iowa State University. He later taught at the University of Iowa, the Massachusetts Institute of Technology, the University of Michigan and the University of Minnesota.

Before joining the New School, he was professor of psychology at Stanford University from 1955-68.

Festinger is survived by his wife, Trudy, two sons, a daughter, a stepdaughter and three grandchildren.