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HARVEY CARR 



the head was placed at X when a choice of the left exit was 

 demanded and at Y when the right exit constituted the correct 

 response. The animals were thus compelled to start from two 

 distinctive positions of such a character that a correct response 

 necessitated a diagonal course from each position to the appro- 

 priate exit. The percentage of correct choices for the group 

 under these conditions is represented at A in the graph of fig. 7. 

 2. The rats were now placed at the two positions, X and Y, in 

 such a manner that a correct choice necessitated a direct course 

 to the proper exit. The percentage result for the group is 

 represented by B in the curve. 3. The animals were handled 

 and placed in the usual position by Dr. Vincent. These results 

 are represented in the curve at the points C. 4. The animals 

 were subjected to normal conditions when the left opening 



Figure 7. — Group curve representing the effect of the introduction 



of control tests. 



constituted the correct choice, but whenever the right exit was 

 to be chosen the animals were given a body orientation with 

 the head pointing toward the right instead of to the left as under 

 normal conditions. This orientation of the animal compelled 

 the experimenter to place the rats in position with the left hand. 

 The two choices are thus preceded by two distinctive methods 

 of handling and two different orientations of the body. The 

 results from this test are represented at the points D. 5. The 

 rats were invariably given a head orientation toward the right 

 instead of to the left as with normal conditions. This procedure 

 involved a new method of handling and a new method of turning 

 in starting for the exits. The results of the test are represented 

 at the points E. 



Tests for normal conditions were interpolated among these 

 control experiments. The records secured for these normal 

 conditions are represented in the graph at those points not marked 



