Stanford psychologist Lee Ross hit upon this in 1977. He fashioned a sandwich board emblazoned with the slogan ‘Eat at Joe’s’ and asked randomly selected students to wear it around campus for thirty minutes. They also had to estimate how many other students would put themselves forward for the task. Those who declared themselves willing to wear the sign assumed that the majority (62%) would also agree to it. On the other hand, those who politely refused believed that most people (67%) would find it too stupid to undertake. In both cases, the students imagined themselves to be in the popular majority.
Excerpt from: The Art of Thinking Clearly by Rolf Dobelli