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THE QUARTERLY REVIEW OF BIOLOGY 



may have emerged, (z) the criterion of 

 conscious life in the individual organism, 

 and (3) criteria of psychic levels in infra- 

 human organisms. The futility of specu- 

 lation concerning such problems became 

 more and more apparent, and about 

 191Z a movement to adopt a straightfor- 

 ward objective, or behavioristic viewpoint 

 came to the fore under the leadership of 

 Watson. Since that time, comparative 

 psychology has been attempting to read- 

 just itself to a strictly natural science 

 position as the logical outcome of the 

 Darwinian conception of psychology as a 

 biological science. An account will now 

 be given of the more important theoretical 

 tendencies that led ultimately to the 

 liberation of infra-human psychology 

 from the dominating influence of human 

 psychology and speculative philosophy. 

 The tropism theory of Loeb offered a 

 distinct challenge to the old school that 

 had taken more or less for granted the 

 supposition that even the lowest organ- 

 isms possessed some form of psychic life. 

 Loeb held the elemental component of all 

 psychic life to be "the activity of the 

 associative memory" and maintained that 

 unless an organism could be shown to 

 possess the capacity to form associations 

 its behavior must be considered uncon- 

 scious. "Our criterion," he says, "puts 

 an end to the metaphysical ideas that all 

 matter, and hence the whole animal world 

 possesses consciousness." The logical 

 conclusion is that tropistic and instinctive 

 behavior is wholly unconscious and that 

 such organisms as are incapable of defi- 

 nitely profiting by experience are nothing 

 more nor less than reflex machines. This 

 general point of view was accepted by 

 Beer, Bethe, and von Uexkull (93), 

 Nuel (183), Ziegler (zo, 2.61) and others, 

 and by Bohn (105, 107) in a somewhat 

 modified form. On the basis of this 

 criterion, this group contended that most 



probably the invertebrates generally were 

 devoid of consciousness . At any rate, an 

 adequate account of their behavior could 

 be given in physico-chemical and behavior 

 terms and without reference to any 

 possible psychic life. In much the same 

 vein, Titchener (115) denied consciousness 

 to plants, although accepting the current 

 view that all animal forms are conscious 

 in some sense. 



Bethe 's contention that ants, bees and 

 other insects are mere reflex machines 

 stirred up no little controversy among 

 the entomologists. Wasmann (1x5, zz6), 

 although denying rational intelligence to 

 even the higher vertebrates, insisted on 

 assigning some sort of psychic life to 

 insects, while Buttel-Reepen (108), and 

 especially Forel (131), held that insects 

 give evidence of a relatively complex 

 mental life. Forel went so far as to 

 maintain that their behavior involves 

 memory, associations of sensory images, 

 perceptions, attention, habit formation, 

 and simple powers of inference from 

 analogy. 



The attempt of Loeb and other mech- 

 anists to restrict consciousness to the 

 higher animals on the basis of ability to 

 form associations was brought to naught 

 by experimental results indicating that 

 many, if not all, of the lower organisms 

 have such capacity to some degree. The 

 early work of Jennings, Pier on, Yerkes 

 and others had clearly shown this fact. 

 Furthermore, many writers, including 

 Romanes, Lubbock and Morgan, had 

 pointed out the logical fallacy of denying 

 consciousness to organisms that do not 

 meet an arbitrary criterion of this sort. 



The basic assumption of Loeb, that 

 tropistic, instinctive, and unlearned 

 responses in general are wholly uncon- 

 scious, and hence that consciousness is 

 coextensive with acquired, or intelligent 

 behavior, was called in question on all 



