Solomon Asch (1907-1996) joined Swarthmore's psychology department in 1947. For the next 19 years, he produced work that would confirm his place among the field's leading innovators. Working with accomplished colleagues such as Wolfgang Köhler and Hans Wallach, he established the department as a premiere center of Gestalt psychology.

In 1951, Asch began the experiments for which he is now best known. Those taking part in his studies found themselves sitting alongside several other people. They were all shown a line of a certain length and asked to state which of three other lines matched it. The subjects were unaware that all the other people in the room were imposters who gave blatantly wrong answers. Yet such was the power of conformity that three-quarters of them went along with the obviously false consensus at least once. This technique was a powerful lens for examining social influence and gave rise to decades of research on conformity.