n2 



Journal of Comparative Neurology and Psychology. 



Concerning the statistical values given in connection with 

 this work certain important facts should be noted. First, the 

 reactions are very variable. In fact the variability is so large 

 that, were it not for the analysis of the pairs of reactions, the 

 results could not be presented as conclusive evidence of the in- 

 hibitory or reinforcing influence of stimuli. But the fact that 

 two times in three a visual stimulus almost simultaneous with 

 electric stimulation of the skin shortens the time of reaction to 

 the latter, whereas the same visual stimulus when given half a 

 second before the electric lengthens the reaction-time in at least 

 two-thirds of the cases, justifies us in putting confidence in the 

 averages of the series despite the large probable errors and 

 coefficients of variation. 



The standard deviation of the electric reaction-time is un- 

 usually large because, in averaging, no selection was made from 

 among the results. The apparatus was such as to permit reflex 

 reactions, and as some of these (40 ^ to 70 (?) are included in 

 the series, as well as delayed reactions, the range is often from 

 40 <^ to 500 (?. Arbitrary selection of reactions by limitation of 

 the range did not seem advisable, and I have therefore pre- 

 sented the results as they were taken. Indeed, when we work 

 with voluntary modifiable reactions, instead of with those that 

 are forced, we must not expect either small errors or small 

 variabilities. 



