DISCRIMINATION EXPERIMENT WITH WHITE RATS 165 



The first part of the curve is made by averaging together the 

 averages of the successive 20 trials of each of the four rats; the 

 last part the averages are for 100 consecutive trials. 



The increase of time toward the end of the experiment is not 

 easily accounted for. The age of the rats may be one factor. 

 They, however, were not old but were then only full grown. 

 The weather was warmer, and temperature and humidity may 

 be other factors. The rats A and C were from the first (shown 

 in fig 3) until the last days slower than B and D. For C the 

 time average for the last 80 trials was 30 seconds. There is, 

 then, no correlation between accuracy and speed of response. 

 The rat A was the only one that toward the close of the experi- 

 ment showed a reduction of the average time. Reference to 

 the table which follows will show that the per cent of correct 

 choices for this rat increases remarkably with the last 100 trials. 



Table Showing Average Per Cent of Correct Choices in Discrimi- 

 nation of Stationary and Swinging Lights 



1st 2nd 3rd 4th 5th 6th 7th 



Food at stationary lights: 100 100 100 100 100 100 100 



Rat A 40 40 61 57 69 69 90 



RatB 57.5 52 53 64 58 63 78 



Average 48.2 486 57 60 63.5 66 84 



Food at swinging light : 



RatC 76.5 66 68 71 76 86 86 



RatD 55 68 58 68 68 77 87 



Average 65.7 67 63 68.5 72.5 81 86 



Averages 57 56.5 60 65 68 71 85 



The slowness and difficulty of establishing this discrimination 

 is apparent from the table. 



The error curves (fig. 5 on page 166) show the same slow pro- 

 cess of learning to discriminate and further emphasize the 

 tendency of the rats to go to the moving rather than the still light. 

 The use of only four individuals makes the results less certain 

 than would be the case had a larger number been used. 



The records of rat A have frequent notes, as ' Watching, 

 moving back and forth, swinging or nodding while advancing." 



This diagram of a path taken by A (fig. 6) shows a frequent 

 sort of behavior for this individual, which was being fed at the 

 still light. The starts toward the moving light were frequent 

 and were followed by a pause and a run toward the still light. 

 The swaying or nodding motion, rhythmic with the light, was 



