COMPARATIVE PSYCHOLOGY. Ani mal psychology, comparative psychology and genetic psychology should be defined together and by contrast, first, because they are inti mately related, and second, because there is serious disagreement between popular or current usage and strictly technical usage. Briefly, animal psychology designates certain materials of observation; comparative psychology', a particular scientific method of procedure ; and genetic psychology a particular aim, goal or purpose, namely, geneuc or lustorical descrip tion of mind. These statements may be some what expanded as follows.
Animal psychology actually tneans, in com mon usage, the study of mind in animals ex clusive of man. Logically, it should mean the study of mind in animals (including man) as contrasted with plants, for there appears ade quate ground for assuming that mind exists in plants.
Comparative psychology has long been used as practically synonytnous with animal psy chology, that is, as the study of infrahuman animals. Logically, and by analogy with other sciences, it should mean the application of the method of comparison to the phenomena of mind wherever and however presented for observation. Its meaning in terms of purpose and method should be the same as that of com parative anatomy, comparative physiolo.gy, com parative philology or comparative hterature, namely, the more nearly complete and more profitable knowledge and understanding of a group of facts by comparison thereof with more or less closely related facts. The
problems of origins and of developmental re lations must ever be prominent in a compara tive science. Secondly, the comparative method contributes directly and importantly to genetic description.
Genetic psychology is the study. of the evolu tion of mind (phylogenesis of mind) in plants and animals and of the development or growth of mind (ontogenesis of mind) in individuals. This branch of psychology is definable solely in terms of its primary purpose or aim, which is genetic description. Indeed, genetic psychol ogy is simply the historical aspect of the study of mental life. Animal psychology, as also plant psychology, child psychology, abnormal psychology and social psychology, should con tribute facts to genetic psychology, and com parative psychology should supply special methodological assistance. But genetic psy chology as a special aspect of the general science should be restricted to no particular group of mental facts, to no single method. Instead, it should command all materials and all methods in the interests of a description of the processes of mental development and mental evolution. See ANIMAL PSYCHOLOGY; GENETIC PSYCHOLOGY; PSYCHOLOGY.