124 



XEXOZO UTSURIKAWA 



(c) The inbred females failed to respond 43 times in 116 trials. 



(d) The outbred males failed to respond 52 times in 116 trials. 



(3) The reaction time of the males is extremely variable; that 

 of the females is comparatively uniform. 



(4) The sex difference in reaction time for inbred rats is slightly 

 more than for outbred. 



(5) Reaction time, with certain exceptions, is shorter in case 

 of the second trial (repetition of auditory stimulus) than in the 

 first. Failures to respond are more frequent in the second trial 

 than in the first. 



(6) Individual differences exceed sex and strain differences. 



AMOUNT OF RESPONSE TO AUDITORY STIMULI 



The amount of motor response to auditory stimuli was de- 

 termined by multiplying the maximum length (straight line) of 

 the response curve by the maximum height (straight line). The 

 result is expressed in square centimeters. These measurements 

 are even less reliable than those of reaction time, but again 

 there seems no reason to suppose that the errors are unequal 

 for either the sexes or the strains of rat. 



As previously, the statistical data are arranged in tabular 

 form. They appear in table 5. 



TABLE 5 



Amount of Response to Auditory Stimuli 



Outbred 



Average amount of response for the first and second trials = 7.5 c.c. 



Total number of failures to respond in the first and second trials = 65 



