SOME CURIOSITIES OF THINKING. 725 



It is thus evident that research in experimental i)hysiology has 

 had an extent and an application to human psychology which 

 were hardly dreamed of by the original investigators twenty 

 years ago ; and it is clear that as, little by little, the facts to 

 which I have just alluded have been established, they have been 

 seen to throw much light upon psychological processes, and to 

 make our knowledge of the mechanism of thinking both wider 

 and more precise. 



Secondly : There is another field of investigation from which 

 rich results for mental science have recently been reaped namely, 

 physiological psychology. The determination of the special func- 

 tion of different parts of the brain, and the fact ascertained by 

 anatomists that each of these parts is related to other parts by 

 means of great bundles of nerve fibers which pass throughout the 

 brain in many directions, joining the different functional areas 

 with one another, have led to the study of the association pro- 

 cesses which lie at the basis of most of our thinking. 



Mental images never occur singly, but are usually in close re- 

 lation with other images, the result of simultaneous perceptions. 

 The various qualities of an object perceived by different senses 

 are united in our concept of the object. The beautiful form of 

 the rose, its charming color, its delicate odor, the soft, velvety feel 

 of its petals, and the sharp prick of its thorns all come into my 

 consciousness through various channels, but, being simultaneous 

 in their perception, are all joined with one another in a complex 

 unit the concept ; and when I call to mind a rose, it is not one 

 memory of a single sensation which comes into my consciousness, 

 but it is the associated memory pictures of sight and smell and 

 touch which, by a flash of consciousness, rise together into the 

 mind. And since it is possible to analyze these sensations, it is 

 also possible to trace the association between them. I do not hes- 

 itate to call to mind the appearance of the rose, even though I 

 merely perceive its delicate perfume, and there is hardly a flower 

 whose name is not brought up the moment I see or smell it. Yet 

 this process of calling up the image of the flower from its odor, or 

 of calling up its name when I see it, involves a process of trans- 

 mission of physical impulses from one region of the brain to 

 another a process of which the physiological psychologist has 

 actually determined the time. We measure associations in hun- 

 dredths of a second, and with decided accuracy. The mental act 

 of ordinary single association may be said to occupy an eighth of 

 a second The time of the transmission of these impulses varies 

 decidedly at different periods of life, though it requires no deli- 

 cate apparatus to convince one of the contrast between the quick, 

 acute association of the young man and the slow, uncertain, halt- 

 ing memory of the aged. It has been found by Kroepelm that 



