What makes ideas viral and products spread contagiously? What drives word-of-mouth and online social transmission? Prof. Berger studies social epidemics, or how products, ideas, and behaviors catch on and become popular as well as die out and become abandoned. He has published over a dozen articles in top-tier academic journals and popular accounts of his work have appeared in the New York Times, Wall Street Journal, Science, The Economist, and on National Public Radio.