123 



V. K/J^EKILI'lNT 3: THE IlICLIIffiU PLAlO*;. 



The apparatus used in thiH experiment was the seme 

 ae that used in Txperiinent 2: the Ineliminary Inclined Fltme. 

 The animals were prepared in the same way as for the previous 

 experiment, and began work at the ati;e of seventy days. Sixteen 

 males and fourteen females from the inbred strain were used 

 and, as control, an equal number of males and females from 

 the normal series. Of the inbred rats, fifteen v/ere from the 

 7th generation, fourteen from the 8th and one from the ninth. 

 As the behavior of the sinc^le ninth generation rat was no worse 

 than the average of the Sth her results have been induced 

 in the tables and curves of the 8th generation. The stimulus 

 used in this experiment was bread eoaked in milk. 



Cumulative time v/as used in the earlier trials as 

 in the previous experiment, \7hen the rats be^n to succeed 

 within the half hour, each rat was required to open and enter 

 the food box three times each day. At the end of the third 

 trial it was allowed to feed in the box for five minutes, but 

 was permitted no more food until the completion of the next 

 day's experiment. Each rat was used daiDy until it had learn- 

 ed the problem perfectly, the criterion of perfection being 

 three perfect trials for each of three succesr,ive days. A per- 

 fect trial consisted in rijnning from the entrance to the point 

 of operation on the plane at the rear of the box, opening the 

 door, runninik around and entering the box, all v/ithin four 

 seconds; but, if the time consumed in opening the box after 

 passing the entrance was more than two seconds, or, if the 

 time consumed in entering the box after having opened the door 

 T/ae more than tv/o seconds, the trial was considered a fai3ure. 



