Helmholtz's 'psychological' time experiments
Amongst historians of physiology, it is understood that Hermann von Helmholtz's (1821-1894) work on the propagation speed of nervous stimuli constitutes the beginning of a branch of research that, in the following years and decades, became known as 'nerve and muscle physics' and, in more recent times, has been labeled 'neurophysiology' (Helmholtz 1850a; 1852).
Less widely known is the fact that Helmholtz was interested in the time relations structured by the nervous systems of living beings not just from a physiological but also from a psychological point of view. In fact, at the time at which he performed his time experiments in frogs, Helmholtz carried out similar studies in human beings.
Reference: Schmidgen, Henning. 2003. Helmholtz's "Psychological" Time Experiments.. The Virtual Laboratory (ISSN 1866-4784), https://vlp.mpiwg-berlin.mpg.de/references?id=art10