PERCEPTION. 



135 



Localization by sight .. .. .. .. 0011" 



Distinguishing colour . . . . . . . . 0'012 



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



Distinguishing pitch (high notes) . . . . 0019 



Localization by touch .. .. .. .. 0"021 



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



Localization by hearing (greatest interval) . . 0002 



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 <>t' Rhine-wine increased his reaction- 

 time from 01904" to DL'L'ii'J";! and I have myself observed 

 while shooting thai mi amount of alcohol not sufficient 

 to produce any consciously psychical effects, is apt to make 



■ shool behind one's birds. And here, with reference 



to the persona] equation! I may briefly allude to some 



• Loc. cit., p. 012. f Lor. < it., p. 028. 



