What Drives Development? Nature, Nurture, and Reciprocal Relationships
What are the forces that govern or drive the processes, characteristics, and behaviors that develop across childhood? Basically, these forces are a combination of nature and nurture. The term nature refers to the biological forces that govern development. To a certain extent our development is programmed by the genetic codes we inherit. This biological program unfolds throughout childhood. In some respects, child development can be compared to the blossoming of a flower: A seed sprouts, grows into a fragile seedling, and eventually becomes a mature flowering plant. Nature provides the genetic program contained in the seed—and in the child. By now you know that genes influence the color of your eyes, but did you also know they play a role in determining your height and weight, your level of intelligence, and your basic personality?
Nurture refers to the environmental conditions and supports that influence development. A plant needs sunlight, water, and the proper temperature to grow—and it helps if someone pulls the surrounding weeds and adds fertilizer. Children also need to be nurtured: they need love and support from parents, siblings, extended family, teachers, peers, and other people important in their lives. Children can be greatly affected by how these important people nurture them.
Other elements of nurture include a child's economic and sociocultural environments. Poverty, malnutrition, and a lack of adequate medical care can alter a child's developmental path. Cultural heritage and diversity can enrich a child's life, and the neighborhood where the child lives can determine the schools and peer groups that a child will have.
Throughout history, philosophers and scientists have debated the relative roles of nature and nurture. John Watson, a renowned American psychologist of the early twentieth century, was a strong proponent of the nurture school. He wrote:
[G]ive me a dozen healthy infants, well formed, and my own specified world to bring them up and I'll guarantee to take anyone at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and ancestors (1930/1924, p. 104).
Watson argued that experience and learning—nurture—determined what children would become. But other researchers have disagreed, pointing out that characteristics such as personality are determined more by genetics (nature) than by nurture. Today, however, developmental scientists understand that nature and nurture work together and it is impossible to distinguish their separate effects (Lerner, 2006; Rutter, 2002). Rather than arguing about which one is most important, we are interested in learning exactly how the two factors interact with each other. The interacting effects of nature and nurture are evident in the field of behavior genetics.
In behavior genetics, researchers study the relative roles of nature and nurture in development. By studying twins and adopted children, behavior geneticists have been able to estimate that variability in psychological traits and behaviors, including intelligence, emotionality, and basic personality variables, are approximately 40% to 60% due to variability in genetic inheritance. For example, researchers have shown that IQ scores of identical twins are much more similar than scores of fraternal twins (Bouchard & McGue, 1981). Because identical twins come from the same fertilized egg, their genes are exact copies (give or take a few errors in cell division). However, fraternal twins come from separate fertilized eggs, so they are no more alike genetically than any other sibling pairs. Given the fact that both identical and fraternal twins tend to share similar family and learning environments, scientists attribute the greater similarity in IQ between identical twins to their greater genetic similarity.
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