Time to Think - History of Reaction Time

The Dutch physiologist, Franciscus Cornelis Donders, was the first person to conceive of a way to measure "thinking time", and did so in studies performed in the middle part of the 1860's. The continuation of these studies became a central part of the program of the German physiologist, Wilhelm Wundt, whose laboratory in Leipzig was a major breeding ground of the new discipline of "physiological psychology".

http://serendip.brynmawr.edu/bb/reaction/index.html