Yerkes, Inhibition and Rchifoircuient. 137 



ance to consider the temporal relation of stimuli in any study 

 of the relations of complexes of stimuli to sensory or motor 

 processes. To say that two stimuli were given "nearly simul- 

 taneously" or "within a short interval of one another" does not 

 suffice, for this unmeasured interval may make all the difference 

 between the conditions necessary for reinforcement and those for 

 inhibition. 



5. If the meaning of the above statements in terms ot the 

 neural processes is demanded, only a speculative reply can as 

 yet be given. Of theories of inhibition there are already 

 enough ; what we need is methods by which the neural process 

 may be studied. Until we have more definite knowledge of 

 what occurs in the organism in case of the mutual interference 

 or reinforcement of stimuli it may be well for us to experiment 

 much and speculate little. 



A clear statement of what the neural changes which condi- 

 tion inhibition and reinforcement may be is to be found in a re- 

 cent article on inhibition by McDolGall ('03). So far as this 

 paper is concerned it matters little whether inhibition be "as- 

 similation," "drainage," "competition," or something yet un- 

 named. 



References. 



Bowditch, H. P. and Warren, J. W. 



"90. The Knee-Jeik and Its Physiological Modifications. Jour, oj 

 Physiol., Vol. 9, pp. 25-64. 

 McDougall, W. 



'03. The Nature of Inhibitory Processes Within the Nervous System. 

 Brain, Part 102, pp. 1 53-191. 

 Merzbacher, L. 



'00. Ueber die Beziehungen der Sinnesorgane zur den Reflexbewegungen 

 des Frosches. Arch. f. die ges. Physiol., Bd. 81, pp. 222-262. 

 Wundt, Wilhelm. 



'03. (irundzuge der physiologischen Psychologic. Funfte Auflage, 

 Liipztg. 

 Yerkes, Robert Mearns. 



'03. The Instincts, Habits and Reactions of the Frog. Harvard Psycho- 

 logical Studies, Vol. I, pp. 579-638, (Psychological Review Mono- 

 graph Series, Vol. 4.) 



