The basic idea of Vygotsky that underlies his approach to child development is that its determinants are principally different from the determinants of animals' development. Vygotsky holds that the role of mental processes in both animals and humans is to serve their practical activity (Vygotsky & Luria, 1930/1993). The practical activity of humans, however, is principally different from the practical activity of animals. Animals live in a natural environment, and the goal of their activity is adaptation to that environment. In the course of evolution and natural selection, each species of animal has developed adaptive mechanisms (instincts) that are genetically transmitted from one generation to the next. The behavior of lower animals (invertebrates) is predominantly of an instinctive nature. Vertebrate animals, in addition to instinctive forms of behavior, demonstrate many learned behavioral patterns, which are called conditioned reflexes. In contrast to instincts, which are “the means of adaptation to such environmental conditions that are more or less permanent and stable,” conditioned reflexes are “a much more flexible, delicate, and perfected mechanism of adaptation to the environment, which deals with the accommodation of inherited instincts to the animal's individual, specific environmental conditions” (Vygotsky & Luria, 1930/1993, pp. 24–25). The formation of conditioned reflexes in the course of individual learning represents “a new step” (Vygotsky & Luria, 1930/1993, p. 24) in the development of mechanisms of animals' adaptive behavior.