DISCRIMINATIVE ABILITY OF THE TURTLE 27 



conclusive, since the patterns used are somewhat alike in gen- 

 eral symmetry. 



In the black-white tests discrimination was established with 

 four turtles, while one other turtle failed to show improvement 

 in 220 trials. 



Two turtles learned to discriminate between two series of 

 parallel lines 8 mm. wide, one vertical and the other horizontal 

 in direction, and showed a fair degree of discrimination when 

 these lines were reduced to 4 mm. in width. One of these tur- 

 tles did well with a further reduction of the lines to a width 

 of 2 mm. on each box. 



Two turtles learned to discriminate between two series of 

 parallel horizontal lines 8 mm. and 2 mm. in width respectively.' 

 One turtle learned first to discriminate between two series of 

 parallel vertical lines 8 mm. and i mm. wide, next between 

 lines 4 mm. and i mm. wide, then between lines 4 mm. and 

 2 mm. wide, and finally showed an excellent average of discrim- 

 ination between lines 3 mm. and 2 mm. in width. 



Chrysemys does not learn rapidly. An average taken of all 

 the experiments shows that about 183 trials were necessary to 

 establish discrimination. If one experiment is omitted in which 

 455 trials were given, the average is reduced to 154 trials. In 

 these calculations the three final perfect tests are not counted, 

 neither are tests with reduced lines considered, only those line 

 experiments being taken in which discrimination was first being 

 established. 



Two of the memory tests are surprisingly good but are subject 

 to question, no preference tests having been taken. The third, 

 showing perfect memory two weeks after the vertical-horizontal 

 line tests is unquestionably accurate. These results indicate a 

 fair degree of retentiveness. 



The amount of evidence at hand does not justify general 

 conclusions regarding the relative intelligence of turtles of dif- 

 ferent age or different sex. 



The turtles studied exhibited marked individual differences in 

 disposition and in mental ability. 



More particularly from the results of the line experiments it 

 may be concluded that Chrysemys is able to appreciate differ- 

 ences in the direction of line markings even though the lines be 

 narrow, and differences in the width of lines even though these 



