This volume provides a primarily nontechnical summary of experimental and theoretical work conducted over the course of 35 years which resulted in a developmental framework capable of integrating causal influences at the genetic, neural, behavioral, and ecological levels of analysis. It describes novel solutions to the nature-nurture problem at both the empirical and theoretical levels. Following field observations, laboratory experiments led to the discovery of the nonobvious prenatal experiential basis of instinctive behavior in two species--ground-nesting mallard ducklings and hole-nesting...