478 'Journal of Comparative Neurology and Psychology. 



eration and certainty. Fig. 4 exhibits the characteristic differences 

 in the curves of learning yielded by weak, medium, and strong 

 stimuli. These three curves were plotted on the basis of the aver- 

 age number of errors for the mice which were trained in the experi- 

 ments of set I. Curve ^is based upon the data of the last column 

 of table 3, curve M, upon the data in the last column of table 

 4; and curve S upon the data of the last column of table 5. In 

 addition to exhibiting the fact that the medium stimulus yielded 

 a perfect habit much more quickly than did either of the other 

 stimuli, fig. 4 shows a noteworthy difference in the forms of the 

 curves for the weak and the strong stimuli. Curve JV (weak 

 stimulus) is higher throughout its course than is curve S (strong 

 stimulus). This means that fewer errors are made from the start 

 under the condition of strong stimulation than under the condition 

 of weak stimulation. 



Although by actual measurement we have demonstrated marked 

 difference in sensitiveness to the electric shock among our mice, we 

 are convinced that these differences do not invalidate the conclu- 

 sions which we are about to formulate in the light of the results 

 that have been presented. Determination of the threshold elec- 

 tric stimulus for twenty male and twenty female dancers proved 

 that the males respond to a stimulus which is about 10 per cent 

 less than the smallest stimulus to which the females respond. 



Table 15 contains the condensed results of our experiments. 

 It gives, for each visual condition and strength of stimulus, the 

 number of tests required by the various individuals for the acquisi- 

 tion of a perfect habit; the average number of tests required by 

 the males, for any given visual and electrical conditions; the same 

 for the females; and the general averages. Although the numbers 

 of the mice are not inserted in the table they may readily be learned 

 if anyone wishes to identify a particular individual, by referring 

 to the tables of detailed results. Under set I, weak stimulus, for 

 example, table 15 gives as the records of the two males used 150 

 and 200 + tests. By referring to table 3, we discover that male no. 

 128 acquired his habit as a result of 150 tests, whereas male no. 134 

 was imperfect at the end of 200 tests. To indicate the latter fact 

 the plus sign is added in table 15. Of primary importance for the 

 solution of the problem which we set out to study are the general 

 averages in the last column of the table. From this series of 

 averages we have constructed the curves of fig. 5. This figure 



