ABSTRACT
The concept of levels of psychological capacities of animals, particularly as it relates to phylogeny, was a major pillar in the framework of Schneirla’s science. In his view, schemes of psychological levels “… are a useful means of representing the transition from lower to higher stages of psychological abilities, and are a desirable means of summarizing our knowledge concerning relationships so long as they do not imply an unnatural discontinuity from level to level” (1948). Schneirla elaborated further when he wrote in 1949 (pp. 244, 245): “The term ‘levels’ is a convenient conceptual device for developing a systematic theory of different patterns of adaptation to the given conditions of existence in different organisms,” and “The principle of levels has come into current usage through a recognition of important differences in the complexity, the degree of development, and the independent organization of behavior functions through the animal series”
