Ixxiv Journal of Comparative Neurology. 



The Law of Perception.^ 



Professor Lange shows that each act of perception is composite, 

 consisting, first, in a simple unqualitative shock in consciousness pro- 

 ducing the perception that something has happened. In the second 

 instant there is a recognition of the modality of the stimulus, e. g. 

 that it is optic or auditory. In the third instant the specific peculiari- 

 ties (particular color, etc.) enter consciousness. The rapidity with 

 which these processes replace each other makes necessary experi- 

 mental means to separate them and this is secured by using the psy- 

 chometric apparatus. In the first place the time of the simplest reac- 

 tion is determmed. The simple motor reaction was considered until 

 quite recently as homogenous, but in 1886 Ludwig Lange showed 

 that two forms of such responses occur, depending on whether the at- 

 tention was directed chiefly to the reaction or to the excitation, i. e. 

 muscular or sensory reaction. The former requires much less time 

 than the latter. Thus, with acoustic stimuli the muscular reaction 

 lasts 1525- and the sensory logs ; with tactile stimuli the muscular re- 

 action occupies lyij-and the sensory zoyj- ; with optic stimuli the 

 muscular reaction occupies 22gs, the sensory 297^-. 



According to the view here presented the difference is to be in- 

 terpreted thus : The muscular reaction takes place when the percep- 

 tion of some sort of stimulus is reached while the sensory only occurs 

 when the kind of reaction is distinguished. 



Ludwig Lange, however, explained the difference by supposing 

 that a pre-existing motor innervation was a prerequisite to the shorter 

 reaction time, while the present writer affirms that the sole prerequi- 

 site is the absence of attention to the kind of stimulus. 



In the determination of the next stage it is necessary to select 

 proper subjective and objective conditions of experiment. One must 

 have his attention directed to the stage of complication of perception 

 for which he is to react and the stimuli must be so interspersed with 

 those of a different nature to which he should not respond that the 

 act of perception may not drop to a lower state. 



The perception of acoustic stimuli as distinguished from tactile 

 occupied 192^-, as distinguished from other acoustic, 246^'. In the 

 optic sense the " muscular" reaction, i. e immediate resjionse to the 

 light irritation occupied 2295-, the recognition of it as optic occupied 

 270.?, and the perception of the stimulus as a given color occupied 

 3215 The author attempts to show that the act of judgement is of a 



1 Professor N. I.ange in Intern. Congress of Experimental Psyehology. 



