· 123 American male students were shown a series of lines; the standard line and 3 comparison lines, one of which was the same length as the standard line
· In each test, 7 males would be seated in front of the lines
· All but one of the men were confederates so only one true participant was being tested at a time
· Asch instructed the confederates to unanimously give the same incorrect answer on 12/18 of the trials (critical trials)
· The true participant was always the last but one to answer.