60 WALTER S. HUNTER AND JOS. U. YARBROUGH 



VII 



The Strength of Habit.— Rats 25, 26, 27, 28 and 29, whose 

 learning periods were described in the first section of the paper, 

 were further tested as follows: At the close of the 40 trials at 

 87 1% made on the first h. c. habit, each rat was given control 1 

 on three days alternating with the normal. All of the rats 

 failed to respond correctly in this control. They were then 

 each given two consecutive days on control 2 (buzzer substi- 

 tuted for h. c). In case a rat fell below 80%, a day with the 

 normal stimulus was interpolated. The results are in table 6. 



TABLE 6 

 No. 25 No. 26 No. 27 No. 28 No. 29 



H.C.. 



Con. 2. 

 H. C. 

 Con. 2. 

 Con. 2. 

 H. C 



It will be seen from this that rat 26 did not rate the buzzer as 

 identical with the handclaps and that No. 29 failed also, but 

 on the first day only. No 28 became sick on the third day 

 and was dropped from the tests. At the close of the tests in 

 the above table, Nos. 25, 26, 27 and 29 were immediately started 

 on learning "buzzer to left, right for silence " which was the 

 opposite habit to the extent shown in the table. The progress 

 of learning B in successive fifties was shown in table 5. The 

 very important point that I wish to emphasize is that no one 

 of these four rats learned in less than 770 trials while two were 

 as high as 910 and 920. It took these rats approximately twice 

 as long to break the h. c. habit as it had to form it. The figures 

 are: No. 25, h. c. habit-420, buzzer habit-850 (?); No. 26, 

 h. c. habit-550, buzzer habit-910; No. 27, h. c. habit-320, buzzer 

 habit-770; No. 29, h. c. habit-570, buzzer habit-920. These 

 figures exhibit in a striking manner the tenacity of habits in 

 the rat. The original habit need not be literally broken, how- 

 ever, because in each case a period of retraining reinstated it. 

 The situation is probably more accurately described by saying 

 that the first h. c. habit interfered with the formation of the 

 buzzer habit, although the latter but slightly (if at all) affected 



