THE question of the birth of consciousness as higher forms of life develop has always had a great attraction for scholars in all fields of research. Their findings are not entirely free from subjective speculation, which exerts an influence throughout this borderland of empirical science and metaphysical dogmatism. Fortunately, however, progress in our understanding of animal psychology is by no means dependent on the solution of the problem of how consciousness began to exist.
Psychology may be defined in various ways, but no definition can be satisfactory which does not include its connections with the phenomena of consciousness. As the investigation of such phenomena constitutes a considerable part of psychology, it will not be possible entirely to exclude animal psychology from it. But animal psychology is just as closely connected with zoology.1 A zoology which limits itself to investigating the physical organism of an animal and makes no mention of the processes revealed in the animal's behaviour is deserving of censure as having failed to deal adequately with its subject.2
Thus it is clear that animal psychology is a science which____________________