TEMPERAMENTAL DIFFERENCES IN ALBINO RATS 121 



the time did not permit of the development of a suitable form 

 of apparatus, this plan was abandoned in favor of a less expen- 

 sive and cruder preliminary mode of observation. 



The apparatus finally devised and used consisted of a small 

 blackened rectangular box which rested at one end on two 

 pointed metallic posts and was suspended at the other end by 

 a delicate spring. This box was connected with a kymograph 

 by means of a marking lever so that any vertical movement of 

 the box was recorded on the kymograph surface. The rat was 

 placed in the box and so confined by means of movable parti- 

 tions that it was forced to hold its orientation with head pointed 

 forward toward the writing lever. The front end of the box 

 consisted of a wire screen. On the kymograph three records 

 were written: (1) A time line, indicating fifths of a second; 

 (2) a stimulus line; (3) a response line. 



The only mode of stimulation here reported is the auditory, 

 and for this purpose an electric bell was used. 



The reaction box and stimulus apparatus were enclosed in a 

 large pasteboard box in order that the animal should be some- 

 what protected from disturbing conditions. 



QUICKNESS OF RESPONSE TO AUDITORY STIMULI 



A rat having been placed in the apparatus and allowed to 

 become accustomed to its position, the various parts of the 

 mechanism were carefully adjusted, and when everything was 

 in readiness an auditory stimulus was given for .5 to .6 of a 

 second. After eight seconds, the stimulus was repeated. Then 

 the experimenter waited for an interval of another eight seconds 

 before again presenting a pair of auditory stimuli. 



The quickness of response was indicated by the distance 

 between the point of stimulation on the stimulus line and the 

 point of initial response on the reaction line. The measurement 

 is extremely crude and inaccurate, but so far as may be judged, 

 not more so for the one strain or the one sex than for the other. 

 Where, because of long delayed or indefinite response, it was 

 difficult to decide on the initial point, the reaction was ignored. 



The data of table 4 include the mean or average reaction 

 time for each individual in the first trial, that is, after initial 

 stimulus, and in the second trial, that is, with repetition of the 

 stimulus, the maximal and minimal reaction times, the total 



