I. PITCH-DISCRIMINATION^ 



HISTORICAL 



Se^■eral reports of experimental tests on the audition of the 

 dog have been published. Most of them have been made by 

 physiologists, who were interested not so much in the degree of 

 the animal's discrimination as in the localization of the cerebral 

 centers which govern it. 



Pavloff 's ^ school (notably Selionyi ^) have attempted the de- 

 termination of the dog's sensitivity to differences of pitch, 

 by the saliva-reflex method. Yerkes and Morgulis * have 

 given a comprehensive description in English of this method. 

 Some of the most important points in their article are set forth 

 below. 



The saliva-reflex (secretion of saliva) occurs under two strik- 

 ingly different conditions: when the glands are stimulated by 

 the specific (chemical) stimuli for secretion ; and when the 

 animal is presented with visual, olfactory, auditory or other 

 stimuli, which have been concomitants of direct stimuli of the 

 salivary grands. "The environment of the dog may be said to 

 consist of two sets of properties, the essential and non-essen- 

 tial." Properties essential for a given reaction are those char- 

 acteristics of an object which "regularly and definitely determine 

 the reaction of the organism;" non-essential properties of the 

 object are "those which only in a highly variable and inconstant 

 manner condition the reaction." The chemical property of food, 

 whereby it acts on the receptors of the mouth of the dog, is an 

 example of the essential class; the brightness, color, etc., are 

 examples of the non-essential properties. Reflex responses to 

 "essential" properties are called "unconditioned" reflexes; 



^ From the psychological laboratory of the Johns Hopkins University. 



^ PAVLoff, J. P. The scientific investigation of the psychical faculties or 

 processes in the higher animals. Lancet, 1906, pp. 911-915.. 



^ Selionyi, G. P. Contribution to the study of the reactions of the dog to 

 auditory stimuli. Dissertation. St. Petersburg, 1907. (In Russian.) Method 

 reported by Yerkes and INIorgulis, I.e., below. 



* Yerkes, R. M. and Morgulis, S. The method of Pavloff in comparative 

 psychology. Psychological Bulletin, 1909, pp. 257 ff. 



