DYNAMOGENIC INFLUENCE OF LIGHT 



355 



(F-ds) were presented a flash alone (F) to which the subject was to 

 react, and a sound alone, to which reaction was to be inhibited. 

 Both subjects required a longer time for reaction to (F-ds) than 

 to (Fs-ds) , showing that the combination of sound with flash tended 

 to shorten the reaction-time. 



I confess to some misgivings over Dunlap's belief that this 

 check experiment showed that in the original one, the subjects 



TABLE 1 

 Summary of Dunlap's results 



By P.R. is denoted the probable range of the measurements, as indicated by 

 Chauvenet's criterion; by M, the mean of those measurements falling within the 

 limits of P.R. (a very few measurements were thus excluded); by P.E., the prob- 

 able error of the determination denoted by the subscript; by DI the value of 

 M 8 f-M 8 ; and by D 2 , the value of M P -M FS . The ratio D:PE D gives a means of 

 ascertaining the probability for and against the occurrence of D being due to 

 chance. The values of P.R. are subject to an error of unknown magnitude, as- 

 sumed to be of a secondary order, due to deviation from normality of distribu- 

 tion. It is assumed that the means are normally distributed whether the dis- 

 tributions of the measurements of which they are the means be normal or not. 

 The unit of measurement is 0.001 second. 



