728 COMPARATIVE AND GENETIC PSYCHOLOGY 



house * though they differ in specific interpretation all agree, 

 as the result of independent observation and experiment, that 

 dogs and cats learn, by the repetition of accidentally successful 

 movements, to open difficult fastenings or to find their way through 

 strange ways. Finally, Thorndike, 2 Kinnaman, 3 and Hobhouse 4 

 have experimented on different species of monkeys and have found 

 that they learn more swiftly and with greater accuracy than the 

 other vetebrates to perform relatively complex acts. 



It follows from the results of these investigations that the scope 

 of comparative psychology probably is as wide as that of animal 

 life. No form of animal organisms is a priori excluded, by its 

 structural simplicity, from the group of adaptively reacting ani- 

 mals. Distinctions of behavior and of consciousness, in other 

 words, are not closely parallel with those of structure. Every 

 order of animal life may, therefore, be studied with the possibility 

 in view of discovering indications of non-mechanical, adaptive 

 behavior, and, by consequence, of psychic life. 



The boundaries of comparative psychology are, from this point 

 of view, very wide. If, however, one consider not the number of 

 animals that are conscious, but the nature of their consciousness, 

 then the conception of animal consciousness viewed, thus in in- 

 tension not in extension, shrinks to lesser limits. This pro- 

 blem, the nature of the animal consciousness, can be here discussed 

 in briefest outline only. 



The minimal consciousness which an animal may be proved to 

 have is, as has been shown, the consciousness which accompanies 

 the trial and error type of learning. This process must, therefore, 

 be carefully scrutinized. On its physiological side, that is, so far 

 as observed behavior and inferred nerve-process are concerned, 

 this sort of learning includes the following stages: There occur, 

 first, purely instinctive reactions to environment, for example, 

 the rapid running, hither and yon, of a rat at the entrance of a 

 labyrinth, with food at the centre. Among these different instinct- 

 ive reactions, there chances, second, to occur a successful move- 

 ment one which secures the satisfaction of some instinct, in 

 this case, the attainment of food. In the third place, this move- 

 ment which satisfies the instinct is repeated presumably more 

 than once. The reason for this repetition need not here be dis- 

 cussed. The interactionist would of course explain it as an effect 

 of the pleasure which accompanies the satisfaction of the instinct. 

 The opponent of interaction, while admitting the occurrence of 



1 Mind in Evolution, chaps. 7-9. 



2 The Mental Life of Monkeys, Psychol. Review, Monograph Supplement, xv. 



3 The Mental Life of Two Macacus Rhesus Monkeys in Captivity, Amer. 

 Jour, of Psychology, 1902, vol. xm. 



4 Op. cit. 



