354 H. M. JOHNSON 



Dunlap 4 obtained the times required for a small number of 

 simple reactions from four subjects under the following condi- 

 tions, designated by the symbols in parentheses: to the snap 

 generated in a telephone receiver by the passage of a spark- 

 current through an induction-coil with which the receiver is 

 connected (S) ; to the flask from a helium tube on a diffusing sur- 

 face as a spark current was discharged through the tube (F); 

 to the sound mentioned above, but synchronized with the flash 

 (Sf); and to the flash just mentioned, synchronized with the 

 sound (Fs). 



Dunlap's statistical presentation being somewhat unusual and 

 rather difficult of interpretation, I have summarized in table 1 

 of this report the data which he presents on p. 326 of the original 

 article. 



Two of the subjects, W and D, show a slight retardation of re- 

 action when the flash is combined with the sound (Sf) as compared 

 with the tune required for reaction to the sound alone (S). The 

 effect on these two subjects is sufficient to characterize the 

 average for the group. The magnitude of the effect, however, is 

 small, both absolutely and with respect to its probable error: 

 so that, from such a small group of measurements one can hardly 

 draw a conclusion of which one could feel highly certain. 



The combination of the sound with the flash (Fs) shortened 

 the time required for reaction as compared with the time re- 

 quired for reaction to the flash alone (F). The magnitude of the 

 effect is large and its reliability is very high. From superficial 

 inspection one would suspect that in some of the cases in the (Fs) 

 series, the subject had reacted to the sound instead of the flash. 

 Dunlap does not so interpret the results. His reasons are based 

 in part on the subjects' descriptions of their adjustment to the 

 situation, and partly on the results obtained from two reactors 

 under two other compared conditions; in the first series (Fs-ds) 

 of which two kinds of stimuli were presented: a flash accompa- 

 nied by sound (Fs) with reaction to the flash, and sound alone, 

 to which reaction was to be inhibited. In the second series 



4 Dunlap Knight (with the assistance of G. R. Wells) : Some experiments with 

 reactions to visual and auditory stimuli. Psychol. Rev., 1910, xvii, 301-318. 



