PATTERN-DISCRIMINATION IN VERTEBRATES 191 



he could be kept in direct sunlight most of the day, and used 

 forcible feeding on milk and raw eggs for ten days, during which 

 time his condition began to improve rapidly. He became quite 

 wild as a result of such handling, and I dared not resume work 

 with him until June 15, 1915. On August 1 following, he fell 

 from a steam-pipe six feet from the floor and sustained a par- 

 tial fracture of the right femur and the left tibia. He made 

 a fair recovery, but is still occasionally excited by unusual 

 handling. 



While these accidents render the results somewhat ragged in 

 appearance, they occurred after the preliminary training had 

 been completed. They probably do not affect the validity of 



the results. 



RELATIVE EASE OF LEARNING 



The daily records for the two animals appear in tables 1, 2-A 

 and 2-B. They show a striking difference in the relative ease 

 with which the animals learned the problem. Chick 2 required 

 585 trials, distributed over 58 days, to establish a habit of 

 highly accurate choosing. It should be noted, however, that 

 the bird showed consistent improvement in less than 400 trials. 

 The average percentage of correct responses for the 195 trials 

 given between July 12 and August 17 is 87. The monkey, on 

 the other hand, learned the problem in the first daily series of 

 20 trials, during which he made only two incorrect responses. 

 In learning the first problem — that of plain vs. striate discrimi- 

 nation, the chicken required only 214 trials for establishing a 

 perfect habit, and the monkey required 312. 



TABLE 1 

 Record of Monkey 2 



Width of striae on both fields: 0.780 mm. 



Mean brightness of both fields: 6.24 candles per sq. meter 



Direction of striae on positive (standard) field: horizontal 



Deviation from 

 horizontal of 

 striae on No. of No. of 



Date negative trials correct 



1915 field given responses Remarks 



May 18 —90° 20 18 Incorrect choices, trials 1 and 9 



" 20 —90° 20 20 Not worked on days for which no 



record is given 



June 15 —90° 30 26 Very inattentive first 10 trials 



" 16 —90° 20 20 



" 17 —90° 20 19 



