240 The Dancing Mouse 



with the amount of time which the conduct of the experiments 

 required, rendered it the most satisfactory number. But 

 this statement demands elaboration and explanation. 



Very early in my study of the dancer, I learned that a single 

 experience in a given experiment day after day had so little 

 effect upon the animal that a perfect habit could not be es- 

 tablished short of several weeks or months. Similarly, ex- 

 periments in which two tests per day were given proved that 

 even a simple discrimination habit cannot be acquired by 

 'the animal under this condition of training with sufficient 

 rapidity to enable the experimenter to study the formation of 

 the habit advantageously. Next, ten tests in succession each 

 day were given. The results proved satisfactory, consequently 

 I proceeded to carry out my investigation on the basis of a 

 ten-test series. After this method had been thoroughly 

 tried, I decided to investigate the efficiency of other methods 

 for the purpose of instituting comparisons of efficiency and 

 discovering the number of tests per day whose efficiency, 

 as measured by the rapidity of the formation of a white-black 

 discrimination habit, is highest. 



For this purpose I carefully selected five pairs of dancers 

 of the same age, descent, and previous experience, and gave 

 them white-black tests in series of two tests per day (after 

 the twentieth day the number was increased to five) until they 

 had acquired a perfect habit of discriminating. Similarly 

 other dancers were trained by means of series of ten tests, 

 twenty tests, or one hundred tests per day. Since it was my 

 aim to make the results of these various tests strictly com- 

 parable, I spared no pains in selecting the individuals, and 

 in maintaining constancy of experimental conditions. The 

 order of the changes in the position of the cardboards which 

 was adhered to in these efficiency tests was that given in 

 Table 12. 



