A single example from modern experimental work must suffice to illustrate its characteristics. By Breed, the instinctive feeding behavior of young chicks has been observed, and on the basis of controlled experiments, he is able to affirm that the pecking reaction improves in definite fashion with use, and indeed becomes the basis for complicated feeding habits.
Instinct is being brought into closer and closer relation to habit. It no longer stands apart as something mysterious, God given, un modifiable, but instead as the hereditary or innate factor in a complex system of responses.
Emotions and Their Expressions.— Fear, anger, astonishment, joy, are being studied to day in other animals as they have been studied for years in man. The animal psychologist evidently realizes that he must discover new methods to supplement those of human pyhsi ology and psychology.
Most promising among the innovations is the so-called reflex method, by which the variations of some particular reflex response in connection with emotion-evoking situations are measured. Heart-beat, respiration, salivary secretion and the functioning of various other glands are be ing used by this method. The brilliant Russian physiologist, Pawlow, has perfected a method of using the salivary reflex in the study of the functions of the nervous system, and the method is now being adapted by animal psy chologists to inquiry into the emotional or affec tive responses of various animals.
Modifiability of Behavior or Habit For mation — Loeb and other physiologists and psychologists have held that the ability of organisms to profit by experience is evidence of the existence of consciousness. This cri terion or test of consciousness is no longer widely accepted because of certain obvious weaknesses, but the suggestion of it stimulated observation. It appears from the results which have been accumulated that the behavior of all living beings can be modified more or less mark edly and lastingly. It also appears that the nature of the modification as well as the rapid ity with which it develops varies from organism to organism. Thus, whereas a single stimula tion by a hot object may establish in the human infant relatively permanent avoiding reactions, the less highly organized creature, such as fish or frog, guinea pig or rat, may come to avoid the dangerous stimulus only after a number of repetitions.
Again, experimental results indicate that there are many important kinds of habits in the animal kingdom. Some involve adjustment only to present conditions; others to conditions which are temporally or specially more or less remote. Some are dependent upon the initia tive of the animal; others upon social stimuli. Some are evidently influenced by the results of activity ; others seemingly are not.
There is. no single field of inquiry, not ex cepting the senses, in which animal psychology has made more significant or more widely in fluential progress than in that of the modifia bility of animal behavior, habit formation, memory, imagination, the learning processes. Many new types of method have been devised, and results of obvious importance to education, to medicine, as well as to physiology and psy chology, have been recorded.
The maze method, a contribution of animal psychology to biology, offers the possibility of analyzing the learning process. The sensory discrimination method enables an observer to isolate and measure the values of various im portant factors in habit formation. The im portance of the number and frequency of repe titions of an act, the value of punishments and rewards, the mutual relations of habits and the tendency of training in one direction to facili tate or interfere with effects of other kinds of training are being persistently and success fully investigated.
Ideation and study of ideas, associative processes, thoughts, reasoning, is regarded as difficult. Thorndike undertook the task and achieved remarkably' interesting results, but his lead was not directly followed. Instead, interest turned to the study of the senses and of habit formation. Only recently have the problems of complex behavior of the ideational sort been once more brought to the front.
Various forms of animal behavior, some doubtless ideational, others probably not, have been observed, and initial attempts are being made to analyze them. The methods of re search are of considerable interest and may be briefly described.