a psychologist named Solomon Asch conducted a series of now-famous experiments on the dangers of group influence. Asch gathered student volunteers into groups and had them take a vision test. He showed them a picture of three lines of varying lengths and asked questions about how the lines compared with one another: which was longer, which one matched the length of a fourth line, and so on. His questions were so simple that 95 percent of students answered every question correctly. But when Asch planted actors in the groups, and the actors confidently volunteered the same incorrect answer, the number of students who gave all correct answers plunged to 25 percent.