328 Proceedings of Royal Society of Edinburgh. [sess. 
On the Measurement of Simple Reaction Time for Sight, 
Hearing, and Touch. By Prof. Rutherford, M.D., 
F.R.SS. Bond, and Edin. 
(Read July 10, 1894.) 
{Abstract.) 
Sensori-motor reaction time is the interval that elapses between 
the stimulation of a sense organ and a motor response. The 
physiological process involved consists of {a) an afferent factor, — the 
stimulation of a sensory terminal, and transmission of an impulse 
along sensory nerve fibres to the brain; (^) a psychical factor, 
involving an act of sensory perception and the voluntary production 
of a motor impulse ; (c) an efferent factor, — the transmission of an 
impulse along motor nerve fibres, and consequent contraction of 
muscle. 
To render the reaction simple, discrimination is eliminated from 
the act of perception by repeating the same sensation again and 
again without altering its character ; and choice is eliminated from 
the voluntary act by giving the same motor response again and 
again. In the author’s experiments the motor response was given 
in the usual way by the right forefinger closing an electrical key. 
The stimulus for sight was the movement of a flag attached to a 
lever ; that for hearing w^as a click, given by transmitting an 
induction shock through a telephone ; that for touch was an induc- 
tion shock, or a ' mechanical tap. The moments of stimulation and 
response were recorded on a cylinder, and also on a pendulum myo- 
graph, and the time interval was measured with a chronograph and 
tuning-fork in the usual way. The pendulum myograph, although 
not hitherto employed in such experiments, is very advantageous in 
experiments on hearing and touch. Successive curves are super- 
imposed, so that variations in the time of successive reactions are 
visible at a glance, and can be readily compared and measured. 
The record can be readily photographed and thrown on a screen 
for demonstration. 
