An introduction discusses theories of self-organizing systems including the important concept of canalization, which is taken up in chapters by Mader, Rakic, Kagan, and Suomi. Central to the study of development, canalization encompasses the idea that genetic information supports a self-organizing process that is guided by environmental input but that also provides a set of buffers against abnormal environmental and even genetic information.

Kagan and Suomi describe continuity in developmental processes in humans and in Rhesus monkeys, revealing that in at least one important personality characteristic, response to challenge and stress, the behaviors and physiological correlates are strikingly similar. Scarr investigates the role of adoption and home environment on developmental continuity and shows that to a surprising extent children create the environmental niches they fill.

Kuhl provides additional insight into the nature of the biological and environmental signals controlling epigenetic programs through her work on the development of speech perception in human children. The issue she raises of what is general and what is special in human speech perception and language development bears directly on the open versus closed teaming systems observed by Mader for oscine songbirds. In the most detailed account of the biological and environmental signals controlling epigenesis, Pasko Rakic describes the ontogenetic processes that produce the primate cerebral cortex.