Consider an experiment that was done by Daniel Simons, a psychologist at the University of Illinois. He or a member of his lab would walk up to a pedestrian on the street and ask him or her for directions. While the pedestrian was responding, workmen carrying something large (like a doorframe) would walk between them. As the workmen passed, the experimenter switched places with someone else. Only half of the pedestrians noticed, even though the two people could be quite different.