dren from underprivileged backgrounds to a specialized curriculum focused on thinking skills (Chipuer et al., 1990), and produced considerable improvements on a wide range of tests. Another program, Head Start, is specifically geared to underprivileged children around four years old and is able to document an improvement in test scores over the length of the program. These effects dissipate over time, however, and by the end of grade school, there are no significant differences for Head Start participants over other children from similar environments (Darlington, et al., 1980). However, follow-up studies such as the Perry Preschool study (Schweinhart & Weikart, 1988) indicate that children who participated in such programs as preschoolers are less likely to be placed in special education classes, less likely to be held back in grade and more likely to finish high school. A change in a single gene may change the structure of an organism, but Goodwin (1994) argues that we cannot logically step from this to the idea that genes contain all the information needed to create the structure. Viewing organisms as the sum of their genes is reductionistic: organisms must be studied "as dynamic systems with distinctive properties that characterize the living state" (Goodwin). Development of an organism is an epigenetic process: at every step of development, the next step depends on the organism's current biological state, which is a function of both genetics and environment. Organisms construct their environments, change them, interpret sensory experiences, and change the pattern of variation (Lewontin, Rose, & Kamin, 1984). In humans, mental states affect environments through conscious action; the relationship between human and environment is a dual development of each. Kaye (1992) suggests that "the question of human nature is not simply a biological one, no matter how many genetic correlates of character are discovered." Genes, environment, and t...
