Necessary But Not Sufficent: The Respective Roles of Single and Multiple Influences on Individual Development

I was amazed by Theodore Wachs' knowledge base and scholarship. He surveys a vast and complex landscape to explain just about everything we know about what makes people turn out the way they do. Psychologists such as myself are often called upon to explain why a person ended up in a particular situation, and Wachs' book helps me to answer this question within the limits of today's scientific knowledge while avoiding the temptation to oversimplify by attributing outcome to one or two obvious causes. Wachs explores influences on development ranging from evolutionary and genetic to environmental (both proximal and distal). Even more difficult, he provides a model for integrating multiple influences on human outcome. An amazing and well thought out treatise!

To begin, one of the most striking elements of this book is the disregard of inappropriate parsimony in developmental psychology, an area of research that has traditionally involved an attempt to "boil down" the pertinent influences that affect human development. Wachs, on the other hand, serves his readers a delectable plate full of relevant research findings that point to a much more sophisticated web of relations between a myriad of variables shown to be related to some component of human development. Although such an approach to explaining human development seems a bit overwhelming at first, in addition to the over seventy pages of references he has reviewed to author this book, Wachs' exhaustive review of single and multiple developmental influences is both informative and thought provoking. Wachs divides the book into chapters that each outline a specific area believed to have an impact on development. For example, in chapter two Wachs discusses the influences of both evolution and ecology. Much of the reviewed research suggests that evolutionary influences, such as our own selection processes, may serve as "blueprints" which can be "actualized" by more immediate influences (p. 27). In addition, Wachs outlines the affects of ecological influences on human development and finds such results as the correlation between children living in cold climates, where parents may tightly wrap them in warm clothing, and the restriction of their motor activity and influences on their personality development. In chapter three he acknowledges the necessary influence of genetic, neural, and hormonal factors through a review of a great amount of relevant research. He explains that although genes code for particular characteristics and functions, they have only an indirect impact on human development, as they are associated with the conditions of external factors, such as the proximal and distal environmental influences summarized in chapters six and seven. In these chapters Wachs reviews the influence of external conditions, namely proximal and distal factors, on human development. Some proximal factors having an indirect impact on human development are caregiver beliefs, parental rearing styles, and environmental chaos, which is a comprised of many environmental conditions, such as high levels of noise, lack of both temporal and physical structure in the home, and unpredictability in the child's environment. In comparison, distal influences are associated with more long-standing factors, such as characteristics of culture, social class, and parental work situation. An important point to address here, a point about which Wachs continually warns the reader, is that although such evolutionary, ecological, proximal, and distal factors are necessary influences on human development, none, in and of themselves, sufficiently explain the individual variability in human development. In other interesting chapters Wachs outlines many more fact