Nature & Nurture Dr. Carolyn R. Fallahi
Nature-Nurture • Which is more important? • The Diathesis stress model • We figure out the relative amount of nature (genetics, biology, chemistry) & nurture (environment). • Problem: both diatheses & stressors are on a continuum.
Liability/threshold model • Schizophrenia example. • Genetic liability to Schizophrenia. • Environmental stressors may accumulate over time = total liability. • Cross the threshold = develop the disorder. • Protective factors. • Lesser forms of the disorder.
Study Techniques • Twin Research • Identical versus fraternal twins (monozygotic versus dizygotic) • Shared environmental experiences • Common experiences, e.g. parent’s personality, intelligence, SES status, neighborhood live in, parenting techniques • Nonshared environmental experiences • Child’s own experiences within and outside the family that are not shared with siblings
Epigenetic View • The interaction of heredity and environment. • Heredity directs the kind of environmental experiences a person has. • There is ongoing bidirectional interchange. • For example, the development of hearing and eyesight.
The study of Feral Children • Wild children who have been separated from society. • The Case of Genie. • Other cases.
Behavioral Genetic Studies • Intelligence: overall heritability of IQ scores is about .50 or 50% of the variance is explained. • Identical twins raised together: .86 • Raised apart: .72 • Fraternal twins: .60 & .52 • Biological siblings: .47 & .24 • Biological parent & child: .42 & .22 • Adopted parent & adopted child: .19
Temperament & Personality • Temperament: a set of tendencies to respond in predictable ways. • Buss & Plomin (1984) found .50 to .60 average correlations between temperatment scores of identical twins. The correlations for fraternal twins are about 0.
Psychological Disorders • Schizophrenia: disturbances in logical thinking, emotional expression, social behavior. • Originally: thought due to a cold and inconsistent mother. • Now: concordance rates for identical twins: 48%; fraternal twins 17%. • 1% of the general population has Schizophrenia.