ABSTRACT
The stimulation of the nerves of the gastric glands by the act of chewing and swallowing depends then, to a large extent, upon a psychic factor which starts a physiological process. The physiological activity underlying digestion is thus shown to be a very complex reflex act, involving the co-operation of a number of organic processes, some of which are psychological. Ivan Pavlov's observations on dogs have been verified by several investigators on human beings, at least so far as the effect of tasting pleasant substances are concerned. Anton Julius Carlson emphasizes another phase of this complex psycho-physiological process of digestion— a factor big with psychological meaning. It is the tonic effect of appetite upon the alimentary canal. Training in childhood evidently plays an important role in producing likes and dislikes for food. Barring physiological repugnance, which is far less common than is usually thought, likes and dislikes are due altogether too early environment and training.
