5 ID 



THE QUARTERLY REVIEW OF BIOLOGY 



may be responsive. The protozoa show- 

 only the psychic attribute of excitability 

 and cannot be trained at all; certain other 

 animals ranging from Coelenterates to 

 mammalian forms possess primitive in- 

 stincts and functional memory and are 

 subject to coercive training; a few of the 

 higher animals possess genuine memory 

 and intelligence and are amenable to 

 persuasion. Schneider (105) held the 

 view that consciousness exhibits itself in 

 six progressive stages as follows, the first 

 three stages only being applicable to infra- 

 human organisms: ether, material, sense- 

 quality, form, potency, and will. Kirk- 

 patrick (151) proposed " organ os is" as a 

 common term covering both the neural 

 and psychic factors, and recognizes four 

 progressive types of organosis— vegetative, 

 sensory-motor, representative and abstract 

 thinking. Lukas (168) suggested that 

 the criteria of consciousness be grouped 

 under three general heads as follows, 

 (1) morphological, including structural 

 aspects of brain and sense-organs, (z) 

 physiological, with emphasis upon evi- 

 dences of individual purposiveness and 

 the ideomotor factor in behavior, (3) 

 teleological, covering the significance of 

 various stimuli for the organism. Finally 

 Yerkes G-5Z) has analyzed mental activity 

 into three levels — discriminative, intelli- 

 gent, and rational — corresponding roughly 

 to those of Morgan. He does not, like 

 Morgan, limit the highest level to man, 

 but agrees with Morgan that the lowest 

 level is probably common to all animal 

 forms. 



The most systematic set of criteria 

 offered as a basis for determining the 

 psychic level of organisms was the follow- 

 ing, devised by Yerkes (2.52-): 



I. Structural criteria 

 1. General form of organism (Organization) 

 1. Nervous system (Neural-organization) 

 3. Specialization in the nervous system (Neural- 

 specialization) 



II. Functional criteria 

 1. General form of reaction (Discrimination) 

 z. Modifiability of reaction (Docility) 

 3 . Variableness of reaction (Initiative) 



The above criteria are given in the 

 general order of increasing importance, 

 as diagnostic signs of psychic life, 

 functional signs being of more impor- 

 tance than structural, and the particular 

 sign within each group of more value 

 than the general, although as Yerkes 

 admits, this may not hold in every in- 

 stance. In illustrating the application of 

 the criteria, Yerkes examines the evidence 

 for the sea-anemone and concludes that it 

 shows no certain signs of either intelli- 

 gent or rational consciousness, and prob- 

 ably possesses a psychic life on the lowest 

 level, the discriminative. He questions 

 whether it is not reasonable to suppose, 

 on the basis of such criteria, that the 

 ant "possesses a form of consciousness 

 which is comparable in complexity of 

 aspect and change with the human." 

 Curiously enough, many years before 

 Lubbock (166) had stated the case for the 

 ant in much the same language without a 

 definite set of criteria to guide him. 



No one appeared to question the rele- 

 vancy and usefulness of the concept of 

 psychic levels as thus employed in com- 

 parative psychology. The point was 

 quite generally overlooked that little or 

 nothing would be gained by the mere 

 classification of organisms into two or 

 three rough groups of the types suggested, 

 even if the validity of the criteria em- 

 ployed were granted. The subjectivists 

 did not seem to realize that their first and 

 foremost problem was to make an analysis 

 of the animal consciousness, by the 

 method of analogy, along the lines of 

 human introspective psychology. Nor 

 did it seem to occur to them that, to be at 

 all adequate, such an analysis must 

 reveal to us in terms of our own experi- 

 ence how it actually feels to be this, that, 



