Upon entering a psychology laboratory, you and a small group of other participants are tasked with matching a line to one of three other lines of varying lengths. Participants are asked in succession to state aloud which of these line segments have the same length. Sometimes the others’ choices are the same as yours. But occasionally they all seem to agree with each other but not with you.

When it’s your turn to voice your judgments, do you go along with your peers, or stick with your initial assessment?

It could depend a great deal on where you are from.

This experimental task, which has fascinated psychologists and undergraduates alike since the mid-20th Century, shows that an important fraction of people will conform to the inaccurate responses of their peers. This occurs even when the judgement is easy: when people are alone or answer first in a group, they give the correct answers more than 98% of the time.

Such findings raise two questions. First, despite entering the textbooks as how “people” think, nearly all studies examining this effect were conducted among US students. Yet social commentators, going back to at least Alexis De Tocqueville, have noted that Americans are particularly individualistic and independent. So, are Americans good psychological representatives of Homo sapiens more broadly, as the textbooks imply? Second, why was this result so striking to both researchers and their students?