PSYCHOLOGICAL SCIENCE 75 



and possibly yellow, is very vague, and we do not find 

 definite words expressing the ideas of blue or brown. 



The sensations of hearing, taste, and smell, have 

 been less studied by experimental psychologists than 

 those of touch and sight. The sense of pitch in sound 

 is well known to vary largely in different individuals ; 

 a rough estimate of its delicacy is sometimes formed 

 by ability or inability to hear the squeak of the bat. 

 It may be measured scientifically by testing sensi- 

 bility with any source of sound in which the pitch is 

 under control. 



Here again, the differences noted between the 

 powers of various individuals are probably at the 

 base of many differences of opinion and judgment, 

 believed to have a more intellectual " rationale." 



Passing from direct sense-perceptions to the more 

 recondite powers of the mind, we are met at once by 

 the recognition of the importance of memory. 

 Without memory we should be unable to co-ordinate 

 our different states of consciousness; we should, in 

 fact, lose our personality. 



The tendency of past events, particularly if 

 specially impressed on us at the time, to recur 

 spontaneously, has been termed " perseveration." A 

 thought that haunts us and prevents our sleep is a 

 good illustration of this tendency. 



The form of perseveration differs among individuals. 

 Some recall a complete scene ; others visualise form 



