The Efficiency of Training Methods 241 



At the beginning of the two-test training I thought it pos- 

 sible that the animals might acquire a perfect habit with only 

 a few more days' training than is required by the ten-test 

 method. This did not prove to be the case, for at the end of 

 the twentieth day (after forty tests in all) the average number 

 of mistakes, as Table 42 shows, was 3.2 for the males and 

 3.0 for the females. Up to this time there had been clear 

 evidence of the formation of a habit of discriminating white 

 from black, but, on the other hand, the method had proved 

 very unsatisfactory because the first test each day usually 

 appeared to be of very different value from the second. 

 On account of the imminent danger of the interruption of the 

 experiment by the rapid spread of an epidemic among my 

 mice, I decided to increase the number of tests in each series 

 to five in order to complete the experiment if possible before 

 the disease could destroy the animals. On the twenty-first 

 day and thereafter, five-test series were given instead of two- 

 test. Unfortunately I was able to complete the experiment 

 up to the point of thirty successive correct tests with only 

 six of the ten individuals whose numbers appear at the top 

 of Table 42. That the results of this table are reliable, de- 

 spite the fact that some of the individuals had to be taken out 

 of the experiment on account of bad condition, is indicated 

 by the fact that all the mice continued to do their best to 

 discriminate so long as they were used. Possibly the habit 

 would have been acquired a little more quickly by some of 

 the individuals had they been stronger and more active. 



It should be explained at this point that the results in all 

 the efficiency-of-training tables of this chapter are arranged, 

 as in the previous white-black discrimination tables, in tens, 

 that is, each figure in the tables indicates the number of errors 

 in a series of ten tests. In all cases A and B mark preliminary 

 series of tests which were given at the rate of ten tests per 



