THE INTERFERENCE OF VISUAL HABITS 175 



he seemed about to attain it, the position habit would again 

 appear. This conduct was characteristic of all rats, save that 

 rat No. 15 did master the problem. This error-behavior need 

 not be regarded in its entirety as an interference phenomenon, 

 because it occurs in the course of all difficult problems. How- 

 ever, it is to be remembered that the present discrimination of 

 light from darkness is not a difficult problem. Table 5 gives 

 sample records illustrating the above factual statements concern- 

 ing position habits. 



TABLE 5 

 Diary Records Showing Fluctuating Behavior in Learning Habit No. 2 



Rat No. 4 



April 27 8 



28 9 



29 5 



30 5 



May 1 5 



2 6 



15-22 8,8,8,9,6,6,7,5 



Rat No. 14 

 May 16-28 8, 9, 8, 8, 8, 7, 7, 6, 10, 9, 9, 7, 4 



III 



Rat. No 15 was the only one who mastered habit No. 2. This 

 animal was 68 days old when first tested. He acquired habit 

 No. 1 in 120 trials (tables 1 and 2), was put through the controls 

 and immediately started upon habit No. 2. This was mastered 

 in 420 trials (table 4). A control similar to control 1, used in 

 analyzing habit No. 1, was instituted and proved that No. 15 

 was reacting to the stimulus (light) presented. 



A third problem was then set No. 15, — a test in retention. 

 The rat was put back on habit No. 1, the operator again using 

 as stimulus the 32-c.p. light (shaded as before in habit 1). The 

 rat was tested for 15 days, 10 trials daily. Habit No. 2 per- 

 sisted and interfered with the training on habit No. 1 so that 

 the percentage of correct reactions never exceeded 50 for any 

 10 trials. By the close of the 150 trials a position habit of 

 always going to the left had fixed itself upon the rat with such 

 tenacity that tests were discontinued. 



I have plotted three curves, fig. 2, which present graphically 

 the learning processes detailed above. The curves are con- 



