Current Medical Diagnosis & Treatment in Psychiatry

Major Principles of Ontogeny & Phylogeny

Cairns and Cairns outlined seven principles that characterize the human organism in interaction with the environment over time: conservation, coherence, bidirectionality, reciprocal interaction, novelty, within-individual variation, and dynamic systems. The first principle is that of conservation, or connectivity in functioning across time. Even with all the pressure to change, social and cognitive organization tends to be continuous and conservative. The constraints on the organism and the multiple determinants of behavior lead to gradual transition rather than abrupt mutation. Observers can recognize the continuity in persons across even long periods of time; that is, we know that a person remains the same “person.” For Piaget, who began his career by writing scientific papers on the evolution of mollusks, this within- person continuity principle is consistent with his view that species-wide evolution is gradual. Piaget believed that development within individuals reflects development of the species (ie, ontogeny recapitulates phylogeny).

The second principle is coherence. Individuals function as holistic and integrated units, in spite of the multiple systems that contribute to any set of behaviors. One cannot divorce one system from another because the two systems function as a whole that is greater than its component parts. This fact is another conservative force, because an adverse effect on one part of a system tends to be offset by compensatory responses from other parts of the system. This phenomenon applies to all human biological systems and can be applied to psychological functioning.

The third principle is a corollary of the second: Influence between the organism and the environment is bidirectional. The person is an active agent in continuous interaction with others. Reciprocal influences are not identical; rather, at each stage of development, the person organizes the outer world through a mental representational system that mediates all experience with the world. Nevertheless, reciprocity and synchrony constrain the person, and the relative weight of these constraints varies at different points in development. At one extreme, it is possible to speak of symbiosis and total dependency of the infant on the mother; at the other extreme, behavior geneticists refer to genetic effects on environmental variables (such as the proposition that genes produce behavior that leads to the reactions that one receives from others in social exchanges).

Another corollary of the second principle is the principle of reciprocal interaction between subsystems within the individual. Behavioral, cognitive, emotional, neurochemical, hormonal, and morphologic factors affect each other reciprocally. Mental events have biological implications and vice versa. Even though this principle has been embraced by several areas of biology (eg, ethology, behavioral zoology), psychology and psychiatry sometimes persist in a war between biological and mental camps.

The fifth principle of ontogeny is that novelty arises in development. Change is not haphazard. The forces of reciprocal interaction within the individual and the environment lead not only to quantitative changes in the individual but also to the emergence of qualitatively distinct forms, such as locomotion, language, and thought. These changes represent growth rather than random events, in that previous forms typically remain and are supplemented by novel forms.

The sixth principle of phylogeny is that of within-individual variation in developmental rates across subsystems. Change within a subsystem occurs nonlinearly, as in language development or even physical growth. Some of this nonlinearity can be explained by species-wide phenomena, such as puberty, but much of it varies across individuals. In addition, rates of change vary within an individual across subsystems. Consider two young children, identical in age. Child A may learn to crawl before child B, but child B might catch up and learn to walk before child A. Likewise, child B might utter a recognizable word before child A, but child A might be talking in sentences before child B. This unevenness within and across individuals characterizes development and makes predictions probabilistic rather than certain. Some of the variation is attributable to environmental factors that have enduring personal effects (such as the lasting effects on cognitive achievement of early entry into formal schooling) or biological factors that have enduring psychological effects (such as the effect of early pubertal onset on social outcomes), whereas other factors may have only temporary effects (such as efforts to accelerate locomotion onset) or no effects.

Finally, according to the seventh principle, development is extremely sensitive to unique configurations of influence, such as in dynamic systems. Growth and change cannot be reduced to a quantitative cumulation of biological and environmental units. Also, development is not simply hierarchical, with gradual building of functions on previous ones. Rather, development often follows a sequence of organization, disorganization, and then reorganization in a different (possibly more advanced) form. In physical sciences, this principle is called catastrophe theory, reflecting the hypothesis that during the disorganization, events are literally random. But reor- ganization occurs eventually, in lawful and predictable ways. Dynamic systems models are now being used to describe the acquisition of novel functions such as locomotion and language. In theory, the same models could be used to describe individual differences in development, as in psychopathology. Even though the concept of stage-based development has lost favor because of the global nature and nonfalsifiability of some stage theories, these dynamic-system qualities have been captured in stage-based theories of change.

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