DOES IT TAKE TIME TO THINK? 571 



For the sense of touch there is a discrepancy in the results thus 

 far given by different investigators. According to the best author- 

 ity, it appears that the physiological time in this case is about one- 

 seventh of a second, and less than that of sight or hearing. Some, 

 however, make it somewhat larger than this, and place it midway 

 between those of sight and hearing. 



Having thus found the entire physiological time by many care- 

 fully-prepared experiments, and having previously obtained, as has 

 been briefly pointed out, the value of four of its factors, the value of 

 the remaining two can be readily obtained by subtracting. We 

 should then have the time necessarily employed in purely mental acts 

 of distinguishing or recognizing an event and willing the signal. 



One careful investigator, after experiments in which the event was 

 the sounding of a bell, and the signal was made by pressing with the 

 foot, tabulates the resvilt with the following precision : 



Time occupied (in seconds) by the mechanism of hearing the bell 010 



By the act of perception of the sound and of willing the signal 112 



By the transmission of nervous impulse through the spinal cord and nerve of the leg 



to the foot 088 



By the mechanism of muscular contraction in moving slightly the foot 010 



Total physiological time 220 



This is only slightly more than one-fifth of a second. 



The two mental operations, it will be perceived, occupy somewhat 

 more time than is required for the transmission of the impulse to the 

 foot, and a little more than one-half of the entire time. 



In all the tests thus far given the operation of the mind is as sim- 

 ple as possible. The terms of the problem are reduced to their lowest 

 forms. Upon the simplest kind of a perception, and that expected, 

 the patient is required to exercise his volition in the simplest way. 

 There is no necessity of making comparison between two or more sen- 

 sations, or of deciding between two or more courses of action. 



But in the following experiment the mental acts required were 

 more complex. The patient, upon receiving a slight shock given to 

 the right foot, was to give the signal by moving the right hand, and 

 upon receiving the shock in his left foot he was to give the signal 

 with his left hand. He was left in ignorance upon which foot the 

 shock was to come. It was found that under these circumstances the 

 physiological time was prolonged one-fifteenth of a second beyond the 

 corresponding time where the patient was informed which foot was to 

 receive the shock. In the latter case there was no need of reflection, 

 but in the former he was obliged first to decide which foot was 

 touched, and then to decide upon the corresponding signal. One- 

 fifteenth of a second represented the time required for these acts of 

 the mind. 



A similar test was made for the sense of sight. For a red light 



