2 INDIVIDUAL DIFFERENCES AND FAMILY EESEMBLANCES 



right whirlers. It was also found that there was no ' ' inheritance of 

 individually acquired forms of behavior." Apparently the descend- 

 ants of animals that had been previously trained to learn a certain 

 task were given no advantage over ordinary individuals from un- 

 trained stock. 



G. V. Hamilton in his monograph entitled ' ' A Study of Persever- 

 ance Reactions in Primates and Rodents," 2 found that there were 

 definite types of behavior exhibited by the various subjects he used. 

 These consisted of twenty children, a baboon, four monkeys, and five 

 kinds of rodents, comprising, one mouse, five gray rats, five black 

 rats, ten white rats and six gophers. The reactions of the monkeys 

 and the baboon presented a considerable range of individual differ- 

 ences, which determined the experimenter in the selection of his sub- 

 jects, as indicated in the following quotation : ' ' The marked individual 

 ^differences presented by the five infra-human primate subjects reflect 

 a policy of selecting subjects in whom oddities of general reactive 

 equipment had been observed." Later on in the investigation the 

 author refers to the presence of individual differences, as follows: 

 "When a mammalian is confronted by a series of situations for which 

 he is unable to discover and stereotype a specifically adequate and 

 invariably successful mode of response he tends to vary his response 

 in a manner which is less a species than an individual characteristic." 



The writer has had the opportunity of going over the original 

 data of Basset's work on white rats, 3 and finds that a certain amount 

 of individual difference occurs in the animals he tested. Some ani- 

 mals did consistently better work than others, but as Basset himself 

 points out, his numbers were too few to make possible any conclu- 

 sions from the differences that were observed. 



One might mention a large number of isolated cases where the 

 literature of comparative psychology gives evidence of individual 

 differences. It would not be worth while to treat them here, how- 

 ever, because they generally deal with relatively few animals, and 

 are given merely as side issues of experiments planned to bring out 

 other factors. 



2 Hamilton, "A Study of Perseverence Reactions in Primates and Rodents," 

 Behavior Monograph Series, No. 13, 1916. 



3 Basset, "Habit Formation in a Strain of White Rats with Less than 

 Normal Brain Weight," Behavior Monograph Series, No. 9, 1914. 



