206 The Dancing Mouse 



found in the conditions of their original occurrence. They 

 persist by sheer force of conservatism. They have value 

 only in the light of the circumstances under which they first 

 appeared. Although this is merely a fact of habit formation, 

 it suggests that many of the problems which have puzzled 

 students of behavior for ages may be solved by a study of 

 the history of activity. 



That there are marked individual differences in intelligence 

 in the dancing mice is apparent from the results of the ladder- 

 climbing experiment. No. 1000 learned to climb quickly, 

 and largely by his own initiative ; Nos. 2 and. 6, on the con- 

 trary, learned only by reason of tuition (being put through 

 the required act by the experimenter). It occurred to me 

 that this experiment, since it was difficult for some individ- 

 uals and easy for others, might be used to advantage as a 

 test of imitation. If a dancer which knows how to escape 

 to the cage by way of the ladder be placed in the wooden box 

 with one which, despite abundant opportunity, has proved 

 unable to form the habit on his own initiative, will the latter 

 profit by the activity of the former and thus learn the method 

 of escape ? 



On November 20, Nos. 4 and 5 were placed in the wooden 

 box and left there for half an hour. As they had failed to 

 escape at the end of this interval, they were taken out of the 

 box by the experimenter and returned to the nest-box. 

 November 21 and 22 this test of their ability to learn to 

 climb the ladder was repeated with the same result. On 

 November 23 they were placed in the box with the three mice 

 which had previously been trained to climb the ladder. The 

 latter escaped at once. Apparently the attention of Nos. 4 

 and 5 was drawn to the ladder by the disappearance of their 

 companions, for they approached its foot and No. 5 climbed 

 up a short distance. Neither succeeded in escaping, how- 



