No. W2 | 



INDIVIDUAL 1)1 1 11: U KM I > 



231 



large number of low records, more than the law of prob- 

 ability would warrant. 



In Fig. 5 are given sample practise curves, showing the 

 daily records for two white mice, Nos. 51 and 88, that 

 learned the maze quickly, and for two yellow mice, Nos. 

 20 and 26, that were slow to learn. The arrows at the 

 highest points indicate that the mouse did not pass 

 through the maze. Thus No. 26 only got through on the 

 fifth trial and failed in the eleventh, fifteenth and six- 

 teenth trials. 



The mean variation for the entire group of 90 mice was 

 found to be 35.6. This means that any mouse picked at 

 random from the mixed group would be likely to vary 

 from the average by 35.6 seconds. In order to find 

 whether mice of the same litter varied less than unrelated 

 individuals, the mean variations for each of the 18 fami- 

 lies was calculated, and these when weighted for size of 

 family were found to be 20.2. The resemblance in be- 

 havior between mice belonging to the same litter was con- 

 sequently nearly twice as great as between unrelated indi- 

 viduals. This corresponds to a coefficient of correlation 

 in the neighborhood of 0.5 for brothers, as found by Pear- 

 son, Thorndike and others. 



TABLE VI 

 Averages for Sex Differences 



In Table VI, the males and females are grouped sepa- 

 rately, and their average times and errors are given. In 

 both groups of (mainly) white individuals, with 32 males 

 and 31 females, and in the group of (mainly) yellow mice, 

 with 15 males and 12 females, the times for the females 

 are on the average slightly shorter, but the differences fall 

 within the limits of the probable error and indicate that 

 there are no sex differences in this kind of behavior. 



