PEECEPTION. 135 



Localization by sight . . . . . . « . 0*011'' 



Distinguishing colour . . . . . . . . 0"012 



Localization by licaring (least interval) .. 0*015 



Distinguishing pitch (high notes) . . . . 0'019 



Localization by touch . . . . . . . . 0021 



Distinguishing pitch (low notes) . . . . 0'034 



Localization by hearing (greatest interval) . . 0062 



If a greater number of alternatives are allowed by the ' 

 preconcerted arrangement, a still longer interval is required 

 for the response. 



The time required for perception in the case of all the 

 senses varies with different persons, and, under the name of 

 "personal equation," has to be carefully determined by 

 astronomers. It is increased by old age, sundry kinds of 

 sickness, and sundry kinds of drugs. But it is not neces- 

 sarily less in young people full of vitality than it is in young- 

 people of less vigorous or lively temperaments. According 

 to Exner, persons who are accustomed to allow their ideas to 

 run slipshod are relatively slow in forming their perceptions, or, 

 at least, have a long reaction-time between receiving and re- 

 sponding to a stimulus. He gives the following table to 

 show the difference in the reaction-time of seven indi- 

 viduals : — * 



Concerning the effects of drugs it is enough to say that 

 Exner found two bottles of Ehine-wine increased his reaction- 

 time from 0-1904^' to 0-2269'' ;t and I have myself observed 

 while shooting that an amount of alcohol not sufficient 

 to produce any consciously psychical effects, is apt to make 

 one shoot behind one's birds. And here, with reference 

 to the personal equation, I may briefly allude to some 



* Loc. cit., p. 612. t Loc. cif., p. 628. 



