THE DYNAMOGENIC INFLUENCE OF LIGHT ON 

 TACTILE DISCRIMINATION 1 



H. M. JOHNSON 



This paper reports a minor study made at the Nela Research 

 Laboratory in 1916. It was incited by interest in the question 

 of one sensory process tending to reinforce or to inhibit another 

 sensory process belonging to a different mode. 



A single commonplace illustration may suffice to fix the prob- 

 lem. It is often asserted that a smoker cannot tell in the dark 

 whether his tobacco is burning or not. The assertion is somewhat 

 too sweeping. However, a fairly large group of smokers casually 

 interviewed by the writer reported unanimously that they do 

 not enjoy smoking in the dark; and that they cannot experience 

 some of the gust able and olf actable qualities of the smoke unless 

 they can see it. Certainly such is the case with the writer, who 

 smokes habitually and heavily. 



HTSTOBICAL 



The historical notes given below are necessarily incomplete. 

 For some two years the present writer has not had access to lit- 

 erature on the topic, nor even to old historical memoranda pre- 

 pared by himself, which are stored with his household effects. 

 His present duties probably will not permit of further examina- 

 tion of the literature for some time to come. Interested readers 

 are urged to find the original sources for themselves. 



James 2 writes as follows: 



The whole neural organism, it will be remembered, is, physiologi- 

 cally considered, but a machine for converting stimuli into reactions; 

 and the intellectual part of our life is knit up with but the middle or 



1 This paper from the Nela Research Laboratory, National Lamp Works of 

 General Electric Company, Nela Park, Cleveland, Ohio. 



2 James, William: Principles of Psychology, ii, 372 ff. New York, Henry Holt 

 & Co., 1890. 



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