In addition to describing the course of child development, each theory takes a stand on a major issue about its underlying causes: how to characterize the relative influence of genetic and environmental factors in development? This is the age-old nature–nurture controversy. By nature, we mean the hereditary information we receive from our parents at the moment of conception. By nurture, we mean the complex forces of the physical and social world that influence our biological makeup and psychological experiences before and after birth.
Although all theories grant roles to both nature and nurture, they vary in emphasis. Consider the following questions: Is the older child’s ability to think in more complex ways largely the result of a built-in timetable of growth, or is it heavily influenced by stimulation from parents and teachers? Do children acquire language because they are genetically predisposed to do so or because parents intensively teach them from an early age? And what accounts for the vast individual differences among children in height, weight, physical coordination, cognitive abilities, personality traits, and social skills? Is nature or nurture more responsible?