1960s, psychologists Stanley Milgram, PhD, Leonard Bickman, PhD, and Lawrence Berkowitz, EdD, demonstrated social influence by having a group of people on a busy New York City sidewalk gaze up at nothing in the sky. When one man looked up at nothing, only 4 percent of passersby joined him. When five people stood on the sidewalk looking up at nothing, 18 percent of passersby joined them. And when a group of 15 gazed upward, 40 percent of passersby then joined, nearly stopping traffic in one minute