THE CHICAGO EXPERIMENTS WITH RACCOONS 171 



were "strung" on their supporting pivot in any order in which 

 they were picked up. We did not remove them from the room 

 in which the raccoons were kept and we generally found them 

 scattered about the room. The levers were all alike so far as 

 we could detect, until having split one, we replaced it with one 

 having a "new" appearance. This should have brought a new 

 type of result if the animals were responding to the appearance 

 of the levers. 



It is true that this change of card position is mentioned briefly 

 at the outset of the experiments instead of within the portion 

 on which the Chicago experiments were based. But was no 

 further precaution taken which was described on the final pages 

 of report ? On page 259, Table 11,1 record that for two hundred 

 trials the threes were "shown twice." Since this has been un- 

 noticed or misunderstood let me explain it. It means that I 

 would show red, red, red, red, red, red, and the animal must stay 

 down through it all. Then came white, orange, red, and only 

 then would the animal climb up on the high step to be fed. 

 Thus nine movements were made, and all the levers were used. 

 Then followed white, orange, red, and the animal reacted posi- 

 tively and was fed. Thus he could hardly have been responding 

 to alternate threes, or to lever position. Note also that there 

 was an abrupt transition from showing the cards by threes to 

 showing them by sixes. Yet the animal gradually learned to 

 discriminate in this complicated experiment in which all factors 

 were different, except the colors of the absent cards. I describe 

 this showing the cards by sixes at the bottom of page 258, and 

 refer to it as "while you raise three or even six colors, again on 

 page 261." Perhaps tiiis detailed account of the precautions 

 taken to guard against discrimination by threes, and against 

 discrimination by position will serve to convince the reader that 

 the experiments were not so careless or hasty as my critics 

 have supposed. 



But it is further assumed that I mixed the experiments in 

 which the experimenter manipulated the levers with those in 

 which the animal was permitted to claw at them. The two types 

 of experiment were separated by months. My paper states 

 (p. 233) that no tendency to claw at the levers appeared for 

 six weeks of the first type of experiment. After it did appear, 

 clawing at the levers was not permitted until we had learned 



