PSYCHOLOGY, COMPARATIVE. This article deals with Comparative Psychology in its biological aspects. The aspect of the subject from the pure psychologist's point of view will be found under COMPARATIVE PSYCHOLOGY. In everyday life we are accustomed to look upon the behaviour of animals in the same way as we judge the actions and conduct of our fellow men. We do this as if the actions of animals were dictated by a conscious ness such as we know from our own experience. In this way we attribute to animals sensations, perceptions, ideas, feelings and impulses, dictated by will. We suppose that these faculties control the behaviour of animals as they do our own actions. The driver talks to his horse, the sportsman to his dog. We say that the worm writhes with pain, the moth flies into the flame out of curiosity, the dog is faithful, the serpent false. The hen which has acted as foster-mother to ducklings looks on with anxious feelings as the young take to the water. And the aquarium naturalist main tains that mussels, sea-snails, starfishes or sea-anemones, feel happy when they move or expand in the fresh water he has given them. This common-sense view, which represents the natural atti tude of unprejudiced man to animals, has been usual from the earliest days. Savages and primitive peoples to-day feel them selves closely related to animals. On such a conception of the relationship of the minds of animals to those of men reposes the widespread belief in a transmutation of souls with intermediate stations in animals, the so-called metempsychosis.
Since ancient times, however, there have always been investiga tors who opposed this anthropomorphic conception of animal behaviour. Descartes maintained that animals are mere ma chines, moving purely as automata in response to stimuli received. But above all it is modern advances in science which have caused men to study the behaviour of animals more closely and more critically. The nervous system and the sense organs have become better known. The rising science of physiology, concerned with the functions of living organisms, has been able to show that many actions of animals can be submitted to a scientific study and to a causal explanation. Thus it came about that at the end of
the 19th and beginning of the 2oth century, a number of workers, such as Beer, Bethe, von Uexkiill, maintained that the behaviour of animals is solely a subject for physiological research. Accord ing to these and other more recent workers, the concern of science in studying animal behaviour should be strictly limited to the investigation of visible movements and of their causation. One of the principal reasons why these researchers disagree with the anthropomorphic view-point sketched above is that objectively we can never obtain information about the inner life of animals, i.e., about the phenomena of consciousness going on in their minds.
Indeed, the same thing is really true for the conscious life of our fellow men. For from direct experience we only know our own conscious self. But since our fellow men in like situations behave as we do, therefore we conclude by analogy that they think and feel just like ourselves. Further, they tell us the same thing in speech, so that the conclusion by analogy seems all the more sure. The science of human psychology is founded on these facts. But the behaviour of animals leads to a similar analogy, especially the behaviour of those animals most nearly related to man and of those in whose ways man has most confidence, since they sur round him as his household animals. For this reason comparative psychology, which is concerned with the origin of human conscious phenomena in children and lower human races, is led to deal with such analogies in animals when it is seeking, in the animal, phylogenetic antecedents of the human mind. And so, with the coming in of the present century, a new science has arisen, the goal of which is to study animal behaviour, in particular such phenomena as resemble those connected, in man, with particular mental occurrences.