AP Psychology

## Nature and nurture Every behavior and mental process comes from a body that has both an inherited starting point and a history of experience. **Heredity**, often called nature, means the genetic and predisposed characteristics that influence physical, behavioral and mental traits. **Environment**, often called nurture, means the external factors a person experiences, such as family interactions, education, diet, culture and peers. Neither works alone. A child may inherit a tendency toward a quick temper, for example, but whether that tendency shows up as aggression depends on how the people around the child respond to it, so the two sets of factors interact and shape the outcome together. Psychologists therefore rarely ask whether a trait is "genetic or learned". They ask how much of the variation between people in a trait is linked to differences in heredity and how much to differences in environment, and how the two combine. ### Studying the effects of genes Genes cannot be manipulated in people, so researchers rely on natural comparisons between relatives. These are non-experimental designs, which means they can show that a trait runs in families but cannot by themselves prove what causes it. - Twin studies compare identical twins (who come from one fertilized egg and share essentially all of their genes) with fraternal twins (who come from two eggs and share, on average, about half of the genes that differ between people). If a trait is influenced by heredity…