252 The Dancing Mouse 



to do so. As it did not lend itself readily to quantitative 

 study, no attempts were made to measure the duration of 

 this particular habit. At best the climbing of a wire ladder 

 is of very uncertain value as an indication of the influence of 

 training. 



Similarly, the persistence of habits has been forced upon 

 my attention day after day in my various experiments with 

 the mice. It is obvious, then, that the simple fact of memory 

 is well established, and that we may turn at once to an exami- 

 nation of the facts revealed by special memory and re-learning 

 experiments. 



The visual discrimination method, which proved invalu- 

 able as a means of measuring the rapidity of habit formation, 

 proved equally serviceable in the measurement of the per- 

 manency or duration of habits. Memory tests for discrimi- 

 nation habits were made as follows. After a dancer had 

 been trained in the discrimination box so that it could choose 

 the correct electric-box, white, red, blue, or green as it might 

 be, in three successive daily series of ten tests each, it was 

 permitted to remain for a certain length of time without 

 training and without opportunity to exercise its habit of 

 visual discrimination and choice. At the expiration of the 

 rest interval, as we may designate the period during which 

 the habit was not in use, the mouse was placed in the dis- 

 crimination box under precisely the same conditions in which 

 it had been trained and was given a series of ten memory 

 tests with the box to be chosen alternately on the right and 

 on the left. In order that the entire series of ten tests, and 

 sometimes two such series given on consecutive days, might 

 be available as indications of the duration of a habit, the 

 mouse was permitted to enter and pass through either of the 

 electric-boxes without receiving a shock. Had the shock 

 been given as punishment for a wrong choice, it is obvious 



