Q.'Development is influenced by an interplay of heredity and environment; neither works in isolation.' Explain this statement with two examples from the chapter.

Development is always the joint product of genotype (inherited genetic material) and environment interacting together, never the result of either acting entirely alone. …

The statement that development is influenced by an interplay of heredity and environment, with neither working in isolation, is a central theme of the chapter's discussion of Factors Influencing Development, and can be illustrated with two clear examples drawn directly from it.

The first example concerns height. The chapter explains that an individual with genes predisposing them toward 'short' height will never grow taller than their genetic ceiling allows, even if placed in a very good nutritional environment. This shows that genes set an outer limit on development that environment, however favourable, cannot exceed — but it also shows environment is not irrelevant: within the limit set by the genes, the specific height a person actually reaches (their phenotype) still depends on nutrition and other environmental factors. Neither genes alone (which only set a range of possibility) nor environment alone (which cannot push past that range) fully determines the outcome — the actual, observed characteristic is the joint product of both operating together.

The second example concerns Sandra Scarr's (1992) account of how parents shape their children's environment. Scarr observed that the environment parents provide for their children is itself shaped, to some degree, by the parents' own genetic predispositions. For instance, parents who are themselves intelligent and enjoy reading — traits with a genetic component — are likely, because of this very disposition, to provide books and reading opportunities at home for their children; their children, as a result, often grow up to be good readers themselves. Here, it becomes difficult to cleanly separate 'heredity' from 'environment' at all: the child's genes (inherited from reading-inclined parents) and the child's environment (a book-rich home, created by those same parents partly because of their own genetically-influenced interests) are working together, each reinforcing the other, to produce the outcome. …