460 PHYSIOLOGY 



involved in determining whether the stimulus is on the right side, and there- 

 fore should be followed up as agreed, adds considerably to the length of the 

 reaction time (on an average -066 sec.). It is possible to complicate the 

 dilemma to almost any extent. Thus the experiment may be so arranged 

 that either a red or a white disc appears and the subject has to react with 

 the right hand to the red disc and with the left hand to the white disc. In 

 such an experiment the reaction time was found to be 0*154 sec. longer than 

 the simple reaction time. A still more complex process would be involved 

 in the experiment in which a word was spoken, and the subject had to speak 

 some other word which had some association with the word which formed the 

 stimulus, e.g. horse mammal ; paper pen, &c. In such an experiment 

 the reaction time was found to be as long as 0'7 to 0-8 sec. 



We see that the recording of the time of occurrence of any physical event 

 can only occur after a certain lost time, which represents the observer's 

 reaction time for the stimulus in question. This only applies, however, 

 to movements carried out in response to single stimuli, or to stimuli repeated 

 at irregular intervals. When the stimuli are rhythmic the lost time only 

 applies to the first one or two of the stimuli. The observer or subject is 

 conscious of the interval elapsing between the physical event and his reaction, 

 and anticipates the later stimuli so that his reaction becomes synchronous 

 with the stimulus. This synchronism of stimulus and reaction characterises 

 all ryhthmic movements, such as dancing or the playing of an orchestra in 

 time with the beat of the conductor's baton. 



