The lip key (pictured to the right) was a device used in a variety of early studies in psychology, particularly reaction-time experiments. It consists of metal plates separated by a spring. Connected to a timing device such as a chronoscope, and a power source (typically a wet battery) the lip key was placed in the mouth and held between the lips to create an electrical circuit. When the subject opened his or her mouth the circuit would break stopping the timing device.
Keys of all kinds were common in psychological laboratories in the early 20th century. Manual finger keys (such as a telegraph key) were popular instruments as were Ernst Meumann’s biting key, voice keys by Roemer, WilhemWundt, James McKeen Cattell, and others. There was even an eyelid key.
Cattell (1860-1944) introduced the lip key in 1886 when he was still Wundt’s assistant in Leipzig, Germany. It was used in his classic study, “The Time Taken Up by Cerebral Operations” published in Mind (1886). A lip key was also used by Hill and Watanabe (1894) to examine differences in sense and muscle reactions to sound.
A 1924 experiment on delayed understanding of the meaning of words spoken in one of the experimenter’s Texas drawl (Wilson and Weld, 1924) described a typical use of a lip key in an experiment, “The apparatus consisted of a lip key, a stop-watch placed in Edward B. Titchener’s controller, and a telegraph key, connected in such fashion that the watch began ticking when E touched the telegraph key, and stopped when O released the lip key.” (p. 451) In this way, the experimenter (E) could time the subject’s (O) response time to understanding the meaning of a word. The researchers used these data to conclude that a delayed meaning was present 38 percent of the time and no meaning occurred 9 percent of the time.
Reaction time experiments played an important role in early psychological research on individual differences. Today, reaction time studies are much more concerned with cognitive processes, and technologies like the microprocessor have replaced the lip key. ♦
Cattell, J.M. (1886). The time taken up by cerebral processes, Mind, 11, 220-242.
Wilson, M. V. & Weld, H.P. (1924). Delayed meaning. The American Journal of Psychology, 35, 450-453.
Watanabe, R. (1894). Two points in reaction-time experimentation. The American Journal of Psychology, 6, 408-412.