CHAPTER XVI 

 THE DURATION OF HABITS : MEMORY AND RE-LEARNING 



THE effects of training gradually disappear. Habits wane 

 with disuse. In the dancer, it is not possible to establish 

 with certainty the existence of memory in the introspective 

 psychological sense ; but it is possible to measure the efficiency 

 of the training to which the animal is subjected, and the degree 

 of permanency of habits. The materials which constitute 

 this chapter concern the persistence of unused habits, and 

 the influence of previous training on the re-acquisition of a 

 habit which has been lost or on the acquisition of a new habit. 

 For convenience of description, I shall refer to certain of the 

 facts which are to be discussed as facts of memory, with the 

 clear understanding that consciousness is not necessarily 

 implied. By memory, wherever it occurs in this book, I 

 mean the ability of the dancer to retain the power of adaptive 

 action which it has acquired through training. 



I first discovered memory in the dancer, although there was 

 previously no reason for doubting its existence, in connection 

 with the ladder-climbing tests of Chapter XII. In this ex- 

 periment two individuals which had perfectly learned to escape 

 from the experiment box to the nest-box by way of the wire 

 ladder, when tested after an interval of two weeks, during 

 which they had remained in the nest-box without opportunity 

 to exercise their newly acquired habit, demonstrated their 

 memory of tl>e method of escape by returning to the nest-box 

 by way of the ladder as soon as they were given opportunity 



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