INHIBITION AND REINFORCEMENT OF REACTION 

 IN THE FROG RANA CLAMITANS. 



By Robert M. Yerkes. 



[From iht Harvard Psychological Laboratory^ Hugo Munsterberg, Director.) 

 GENERAL PROBLEMS AND METHODS. 



An investigation of the time relations of neural processes 

 in the frog, which began with the determination of simple reac- 

 tion-time (Yerkes, '03. p. 598 et seq.), has now been extended 

 to a study of the influence of complication of stimuli on time 

 of reaction. In this report an attempt will be made to present, 

 in summary, certain results which contribute somewhat to 

 our knowledge of inhibition {^Hemmung) and reinforcement 

 i^Bahnung)} 



Attention was called, in the paper referred to above (p. 

 62'j et seq.), to the inhibition, by visual stimuli, of visible 

 motor reactions to auditory stimuli, as well as to the apparent 

 reinforcement, by an auditory stimulus (tuning-fork sound), of 

 reactions to visual stimulation by a moving red disc. These 

 observations led to a more detailed and systematic study of the 

 influence of complication of stimuli, so far as reaction-time is 

 concerned. 



The work thus far done includes studies of (i) the effect 

 of stimulation by increase in light intensity upon reaction-time 

 to electric stimulation of the skin, (2) the effect of an auditory 

 stimulus upon electric reaction-time, (^3) the effect of visual 

 stimulation by the appearance of a moving finger, (a) when 

 shown almost simultaneously with the giving of the electric 

 stimulus, and (b) when shown a considerable interval (at least 



' This work will be published in detail, in connection with other results, in 

 Volume 2 of the Harvard Psychological Studies. 



