Nature vs Nurture One of Psychologys Greatest Debates

Nature vs. Nurture One of Psychology’s Greatest Debates

Learning Objectives Students should be able to: Describe what is meant by genetics and behavior genetics Differentiate between genes, chromosomes and DNA Describe what is meant by phenotype, genotype, dominant, and recessive genes Describe how kinship studies such as family, twin and adoption studies are sources of information about the effects of heredity Discuss the social implications for research in behavior genetics

Nature vs. Nurture • One of the longest standing debates in psychology • Psychologists today mostly acknowledge that both play interacting roles • Genetic inheritance helps shape your biological makeup

Heredity – one’s biological structures and processes transmitted from generation to generation. One’s NATURE Genetics: the study of how living things pass on traits from one generation to the next Behavioral genetics – field that studies the influence of genetic factors on behavior Bridges the sciences of psychology and biology

Genes and Chromosomes Genes: basic building blocks of heredity. Regulate the development of specific traits Chromosomes: made up of strings of genes Each cell contains 46 arranged in 23 pairs. 23 from mother and 23 from father Sex Chromosomes: The 23 rd pair of chromosomes which determine a person’s sex, male or female. X female; Y male. Chromosomes are complex molecules of DNA

Heredity • Genotype: – our exact genetic makeup, or the set of genes transmitted from our parents. • Phenotype: – Ways in which a person’s genotype is manifested in observable traits. – Genotype has a major influence on phenotype but not the only one. • Dominant gene is one that is expressed when paired genes are different- mask other gene’s effects • Recessive gene expressed only in the absence of dominant genes.

Measuring Genetic Contributions to Behavior in Humans • Kinship Studies: compares the presence of traits and behavior patterns in people who are biologically related or unrelated to help determine the role of genetic factors. • Parents and Children: 50% of their genes in common. Aunts and Uncles have: 25% overlap with nieces and nephews. • 12. 5% overlap with cousins.

Family Studies • Family Studies: examination of the extent to which a trait runs in intact families. – Should see some phenotypic similarities. – But relatives share similar environments so no definitive evidence just correlational evidence.

Twin Studies • Assess influence of heredity by comparing resemblance of identical twins and fraternal twins – Monozygotic twins (100% genes (genotype)) and dizygotic twins (50% no different than brother or sister) – If MZ twins show greater similarity on a trait than DZ twins a genetic basis for the trait has been suggested. – Good comparison because both identical and fraternal twins are usually exposed to similar environmental influences

Adoption Studies • Adoption studies: examine the extent to which children who are adopted resemble their adoptive parents as opposed to biological parents – When children reared by adoptive parents are more similar to their natural parents in a particular trait, strong evidence exists for a genetic role.

Environment • Is it all in your genes? • The answer is NO! • Don’t oversimplify, environment plays a role • Heredity and experience jointly influence most aspects of behavior

Environment • Three powerful environmental influences – Family – Friends – Culture (collectivist vs. individualist)

Social Implications of Behavior Genetics • What are some of the implications for continued research in behavior genetics?

References Rathus, S. A. (2007) Psychology: Concepts and Connections (8 th Ed. ). Belmont, CA: Thomson Wadsworth. Wade, C. & Tavris, C. (2008). Invitation to Psychology (4 th Ed. ). Upper Saddle River, NJ: Prentice Hall.