ABSTRACT
In the 19th century, psychology evolved into an experimental science and very quickly the introduction of the use of time and more specifically, the measurement of reaction time, became a standard experimental technique. An important contributor to this development was the Dutch scholar F. C. Donders, who in 1868 was professor of physiology in Utrecht. Donders (1868-1869/1969) devised methods for studying what he called "the speed of mental operations." His main hypothesis was that mental processes are embedded in real time and that reaction times could be used to estimate the speed of internal cognitive processes. His work is interesting because it offers a means of describing what is going on "inside our heads" by analyzing cognitive activity into separate stages. The underlying assumption arising from Donders' work-namely the assumption that mental operations can be measured in terms of the time they require-is a central feature of modem cognitive psychology. In fact, to paraphrase Ben Franklin who said "Time is Money," it may be more apt for experimental psychologists to say "Time is Cognition."
