Literary Notices. 471 



feeling; association, apperception, attention; motor impulses; and animal psychol- 

 ogy. "Emerson Hall," by Professor Munsterberg, serves to introduce us both 

 to the book and to Harvard's new psychological laboratory. 



The number and scope of the investigations are too large to admit of compre- 

 hensive treatment in a single review^. We shall attempt to deal here merely with 

 the studies on animal psychology, and the review of even this limited portion of the 

 book must be, of necessity, of a summary character. 



Four investigations are reported under the general heading of animal psy- 

 chology: First, "The Mutual Relations of Stimuli in the Frog, Rana clamata 

 Daudin;" second, "The Temporal Relations of Neural Processes;" third, "The 

 Mental Life of the Domestic Pigeon;" fourth, "Reactions of the Crayfish." 

 The first two are reported by Robert M. Yerkes, the third and fourth by John E. 

 Rouse and J. Carleton Bell, respectively. 



The first paper of Yerkes, as is shown by the title, treats of the mutual relations 

 of stimuli in the frog. In part, the results from these experiments have already 

 been reported upon. It is a distinct gain to the research public, however, to have so 

 interesting a series of facts brought into the compass of a single paper. Yerkes 

 treats here, primarily in a physiological way, of the important phenomena of rein- 

 forcement and inhibition in the reactions of the frog to an electric stimulus, when 

 photic and auditory stimuli are given either simultaneously with the electrical 

 stimulus, or at definite intervals before it. Whether reinforcement or inhibition of 

 the reaction to the electrical stimulus occurs under these circumstances depends upon 

 the temporal relation of the other stimuli to the electric. At the end of the paper, 

 he correlates his own work with that of others and attempts a partial explanation. 



Yerkes' second paper, on the temporal relations of neural processes, is, in our 

 opinion, distinctly inferior to his first. He attempts to answer the following ques- 

 tions: First, "Do reaction-times, in any given animal, range with equal frequency of 

 occurrence from short to long, or are there certain modes (most frequented classes) 

 which indicate definite types of reaction, such, for example, as the reflex, the instinc- 

 tive, etc. ^ Second, "If there is distribution of the reaction-times about oneor more 

 modes, what are the types of reaction indicated thereby ? " Third, " Finally, is reac- 

 tion-time of service as a sign or measure of consciousness ? " By recording the reac- 

 tion-times (Hipp chronoscope) of several hundred reactions of the frog to electrical 

 stimuli of different intensities, and finding the modes of the series for any given 

 intensity of stimulus, Yerkes obtains evidence for the existence of certain types of 

 reaction, and he suggests that this distribution of the reactions around given modes 

 indicates their reflex, instinctive and voluntary character. 



Yerkes goes further and answers his third question in the aflirmative: "Hesita- 

 tion in reaction is commonly accepted as an important sign of volitional conscious- 

 ness in man, consequently, delayed reactions in lower animals are supposed to be 

 indicative of psychic processes." And again; "Reaction time with respect to its 

 two aspects of duration and variability may be used as a sign or criterion of cons- 

 ciousness, for in accordance with the nature of these two sets of facts, we classify 

 acts as reflex, instinctive or voluntary." While Yerkes does not say specifically 

 that he means the above statements to apply to the reactions of the frog, this inter- 

 pretation is forced upon the reader in view of the following sentence taken from his 

 introduction to the paper: "Voluntary reaction-time may be as short as 150 ct or as 

 long as life, in an animal capable of profiting by experience as does the frog. It 

 is preeminently of the delayed type of reaction-time" (p. 575). 



