86 EUPHA FOLEY TUGMAN 



discriminate between the two stimulus areas in order to return 

 to the nest box without receiving a shock. Two of the birds, 

 Male V and Female VI, were required to choose the darker area 

 and the other two birds, Male IV and Female V, were required to 

 choose the brighter area. The two groups of birds were other- 

 wise experimented upon in identically the same manner. 

 Throughout the whole investigation the same order in shifting 

 the lights was given to all four birds. The standard light was 

 shifted to one side or the other at frequent and irregular inter- 

 vals. The order was such that the standard light was on the 

 left side the same number of times as on the right side. 



Table I gives the relative position of the standard light during 

 the first 225 trials. The other positions were similar to the 

 ones shown in Table I. When the standard intensity (.098 

 c.p.) was in the position L (Fig. 1) the letter L was used. That 

 means the standard was on the left. When the standard was 

 on the right (at R, Fig. 1), the letter R was used. Since two 

 birds were trained to go to the darker side L means for them 

 that the darker light was on the left side and the brighter on 

 the right. In the positions marked R the darker light was on 

 the right and the brighter on the left. 



TABLE I 



Position of Standard Light for the First 225 Tests 



Series 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 



Preference L RRRRLLRLL 



1 R RLLRLRRLRRLRLR 



2 L LRLRLLRRRLLRLL 



3 L RLLLRRLRRLRLLR 



4 L RRLRRLLRRLRLRL 



5 L RLLRRLRLRRRLRL 



6 L LRLRRLLRRRLRLL 



7 L LRLLRLRRLLRRLR 



8 L R R L R R L R L R L R L R L 



9 L RLRRLRLLRRLRLL 



10 R R L R L R L L R L R L R R L 



11 R LRLLRLRLRLLRRL 



12 R R L L R L R L R R L L R L R 



13 L R L R L L R R L R L L L R R 



14 L R R L L R L R R L R L R L R 



15 R L R L L R L R L L R R L R L 



The sources of light used were two 25 watt, 110 volt Mazda 

 lamps, which were as near alike in quality of light as the experi- 

 menter was able to judge. The apertures in the stimulus adapter 

 were 6 cm. in diameter. 



