16 INDIVIDUAL DIFFERENCES AND FAMILY RESEMBLANCES 



became ' ' tired ' ' of the problem and lost their adjustment, or in other 

 words, the test had been carried too long; secondly, the following 

 explanation may be given: the drop in the sixth day of the test is 



not significant and represents a chance irregularity which would dis- 

 appear from the curve if a still greater number of animals was used. 

 As there is no evidence to support the first of these explanations, it 



