268 The Dancing Mouse 



example, in the ladder- climb ing experiment No. 1000 dis- 

 tinguished himself for his initiative, whereas Nos. 4 and 5 

 never acquired the habit of escaping from confinement by 

 using the ladder. I noticed, in this test of the animal's ability 

 to learn, that while one individual would be scurrying about 

 trying all ways of escape, investigating its surroundings, 

 looking, sniffing, and dancing by turns, another would de- 

 vote all its time to whirling, circling, or washing itself. One 

 in the course of its activity would happen upon the way of es- 

 cape, the other by reason of the limited scope of its activity, 

 not the lack of it, would fail hour after hour to discover even 

 the simplest way of getting back to its nest, to food, and to 

 its companions. Hundreds of times during the past three 

 years I have noticed important individual differences in ini- 

 tiative in connection with the discrimination experiments. 

 The swinging wire doors which one dancer learned to push 

 open before he had been in the box five minutes, another might 

 not become familiar with through his own initiative for hours 

 or days. In fact, it was not seldom that I had to teach an in- 

 dividual to pass from one compartment to the other by gently 

 pushing him against the door until it opened sufficiently 

 to allow him to squeeze through. Occasionally a mouse 

 learned to pull the doors open so that he could pass through 

 the openings in either direction with facility. This was a 

 form of individual initiative which I had not anticipated 

 and did not especially desire, so I did not encourage its de- 

 velopment, but, nevertheless, at least one fourth of the mice 

 which I experimented with in the discrimination box learned 

 the trick. The other three fourths, although they were used 

 in the box day after day sometimes for weeks, never discovered 

 that they might return to the nest-box by pulling the swing- 

 door through which they had just passed as well as by enter- 

 ing one of the electric-boxes. 



