Response time to unexpected stimuli

Secretaries, while typing, responded to the sounding of a buzzer by reaching to and pressing a button located to the left of their typewriters. The buzzer was sounded without forewarning at irregular intervals, once or twice a week, over a period of six months. The data were analyzed by four week periods (5 subjects, 6 responses per subject). The response latencies decreased systematically over the six-month period. During the final four weeks 90 percent of the response latencies were greater than .51 seconds, 50 percent greater than .61 seconds, and 10 percent greater than .82 seconds. Under comparative control conditions, when the subjects were alerted to the stimuli, the responses were .1-.14 seconds faster.