724 COMPARATIVE AND GENETIC PSYCHOLOGY 



tinuity, and by the conviction gained by direct relations with the 

 higher animals, we do admit with practical unanimity that ani- 

 mals who respond in varied fashion to a fixed environment are to 

 be counted as conscious. 



It will be well to illustrate with more care the exact nature of 

 this criterion of consciousness. It has been described already as 

 the occurrence of adaptive, that is, of varying, reactions. Not 

 only are the movements of animals at this stage discriminative, 

 that is, different for different environments, but they are also 

 varied in the same environment: in other words, though the en- 

 vironment remains unchanged, the animal, far from responding 

 with one fixed movement, reacts with progressively increasing com- 

 plexity and effectiveness. The dogs and cats, for example, in Thorn- 

 dike's experiments, who succeeded in learning to let themselves 

 either out of boxes or into them by unfastening latches of vary- 

 ing difficulty, at first responded to the stimulus of the closed 

 door, by a relatively fixed, indiscriminate response to the entire 

 environment, for instance by clawing at the whole surface of the 

 door. Among these repeated and ineffective movements, however, 

 a specialized action presently emerged, which drew the fastening; 

 and this successful movement was repeated, at first by accident; 

 and the casual repetitions resulted at length in the formation of 

 a new motor response, a variation of the original reaction. Adapt- 

 ive variation of response, as thus described, is it will be ob- 

 served identical with the first stage in the developing conscious- 

 ness of a self, the process of learning through association. 1 This 

 criterion of the presence of consciousness implies thus the existence 

 of a truly developing consciousness. 



In passing, this criterion of consciousness should be distinguished 

 from two others, current in modern psychology. By some psych- 

 ologists, as, for example, by Schneider, the purposiveness of 

 an act, that is, its utility, is made the voucher for its psychic 

 character. There are two objections to this doctrine. In the first 

 place, it defines no n- mechanical actions from the standpoint not 

 of the reacting organism but of the observer; in the second place, 

 it makes the doubtful assumption that there are simple reflex 

 actions which are not purposive. A second criterion of conscious- 

 ness has recently been proposed by Dr. Minot: the ability to 

 "dislocate reactions in time, that is, to delay reactions to a given 

 stimulus." 2 To this, it has reasonably been objected 3 that "un- 

 conscious mechanisms could be constructed and indeed do exist 



1 Cf. p. 716, above. 



2 The Problem of Consciousness in its Biological Aspects, Popular Science 

 Monthly, 1902, vol. LXI, pp. 289 seq., esp. p. 293. 



3 H. S. Jennings, Studies on Reactions to Stimuli in Unicellular Organisms, 

 ix, Amer. Jour, of Physiol., vol. vin, p. 57, 1902. 



