134 Journal of Comparative Neurology and Psychology. 



The fact that the variability of the reaction-time to an elec- 

 tric stimulus in connection with a nearly simultaneous visual 

 stimulus is slightly less than that for the electric reaction-time 

 is worthy of note, but it must be admitted that the difference is 

 not sufficiently large to justify us in laying much stress upon 

 the fact until further work furnishes additional evidence on the 

 point. Clearly enough the greater variability when the visual 

 stimulus precedes the electric by an interval of 0.5" to i.o" is 

 due to the increase in the number of delayed reactions, which 

 in turn we may suppose to be the result of the visual stimulus. 

 For these reactions, moreover, the range is greater than for the 

 electric reaction-time, and a graphic representation ol the dis- 

 tribution of the results shows that the mode is much nearer the 

 500 "' extreme than in case of the simultaneous stimuli series. 



So far as my observations go (and it must be remembered 

 that this research deals primarily with voluntary reactions) the 

 statements thus far made concerning the influence of visual stim- 

 uli upon electric reaction-time hold for refle.x reactions (by 

 which is mtant reactions in from 40 ^ to 70 (?) as well as for the 

 slower more deliberate reactions. If further investigation 

 should confirm the suggestion which ni}- results furnish it would 

 lend additional support to work already done on the nature of 

 the reflex ; for Merzbacher, not to mention the results of sev- 

 eral other investigators, found that x-isual stimulation of the eye 

 of the frog with a colored paper screen increases the extent of 

 the reflex in response to cutaneous stimulation, or in other 

 words, causes reinforcement of the reactior^ ('00, p. 250). As 

 he has not studied the phenomenon with reference to the tem- 

 poral relations of the stimuli, no comparison of his results with 

 those of this paper are possible. 



The literature of inhibition and reinforcement consists al- 

 most entirely of papers on the reflexes of animals, or on the voli- 

 tional process of man, and in no instance have I been able to 

 find any accurate statements concerning the significance of the 

 temporal relations of the stimuli. Wundt ('03, III, p. 443) 

 states, as his belief, that the interference of unlike 

 stimuli is greater than that of stimuli of the same qual- 



