According to the nature advocates, just as a sunflower grows in an orderly way— unless defeated by an unfriendly environment—so does the human grow in an orderly way. The range of environments can be vast, but the nature approach argues that a genetic blueprint produces commonalities in growth and development. We walk before we talk, speak one word before two words, grow rapidly in infancy and less so in early childhood, experience a rush of sexual hormones in puberty, reach the peak of our physical strength in late adolescence and early adulthood, and then physically decline. The nature proponents acknowledge that extreme environments—those that are psychologically barren or hostile—can depress development. However, they believe that basic growth tendencies are genetically wired into humans.

By contrast, other psychologists emphasize the importance of nurture, or environmental experiences, in development. Experiences run the gamut from the individual’s biological environment (nutrition, medical care, drugs, and physical accidents) to the social environment (family, peers, schools, community, media, and culture).