“Here’s another example of the subtleties of persuasion. A large group of students were recruited for what they were told was a market research study by a company making high-tech headphones. They were each given a headset and told that the company wanted to test to see how well they worked when the listener was in motion- dancing up and down, say, or moving his or her head. All of the students listened to songs by Linda Ronstadt and the Eagles, and then heard a radio editorial arguing that tuition at their university should be raised from its present level of $587 to $750. A third were told that while they listened to the taped radio editorial they should nod their heads vigorously up and down. The next third were told to shake their heads from side to side. The final third were the control group. They were told to keep their heads still. When they were finished, all the students were given a short questionnaire, asking them questions about the quality of the songs and the effect of the shaking. Slipped in at the end was the question the experimenters really wanted to answer to: ‘What do you feel would be an appropriate dollar amount for undergraduate tuition per year?’…

The students who kept their heads still were still unmoved by the editorial. The tuition amount that they guessed was appropriate was $582- or just about where tuition was already. Those who shook their heads from side to side as they listened to the editorial- even though they thought they were simply testing headset quality- disagreed strongly with the proposed increase. They wanted tuition to fall on average to $467 a year. Those who were told to nod their heads up and down, meanwhile, found the editorial very persuasive. They wanted tuition to rise, on average, to $646. The simple act of moving their heads up and down, ostensibly for another reason entirely- was sufficient to cause them to recommend a policy that would take money out of their own pockets.” -From, “The Tipping Point” By: Malcolm Gladwell