Chronoscope, 1921-39.

Chronoscope made by the National Institute of Industrial Psychology(NIIP), London, and was used to measure reaction times in pyschological tests, c.1921-1939. A chronoscope is used for measuring small amounts of time, to an accuracy of 1/1000th of a second. They became popular with the emergence of laboratories of experimental psychology in the late 19th century, where they were used to try to determine the speed of thought.