21 

 indication that a greater number of trials will be re- 

 quired before the problem is learned. A retardation in 

 learning is apparently evident. Again the curve for one 

 trial a day shows that little effort was required after 

 the descent of the curve, before the learning was completed. 

 On the other hand greater effort was required after the 

 descent with the three and five trials. This is shown not 

 alone in the greater length of this part of the curves but 

 also their irregularity. This is not true of all individu- 

 al rats, for some learned the problem sooner than others, 

 and, of course, finished sooner, as is indicated by the 

 rapid drop in the curves. A small circle on each of the 

 curves indicates just when the first rat left off learn- 

 ing, and the curve first showing a circle is that plot- 

 ted for one trial a day, the next for three trials and 

 lastly for five trials. A possible cause for the greater 

 number of trials indicated, when three and five trials 



