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The Genetic Contribution to Personality: Understanding Nature vs. Nurture

This chapter explores how heredity influences personality through genetic coding, affecting the brain and nervous system. Research methodologies include studying infant temperament and conducting heritability studies on twins. The text discusses how genetic traits and temperaments are stable, the role of identical and fraternal twins, and the significance of behavioral genetics. Caution is advised in interpreting these findings, as not all traits are equally heritable, and environmental factors also play a crucial role in shaping personality.

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The Genetic Contribution to Personality: Understanding Nature vs. Nurture

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  1. Chapter 2 Section 4: The Genetic Contribution

  2. Nature/Nurture Debate • How can heredity effect personality? • Genes are made up of elements of DNA & they form chemical codes for the synthesis of protein • The proteins affect virtually every aspect of the body • Genes affect personality through their effects on the brain & nervous system of an infant

  3. Measured by 2 Ways • Studying the temperament of infants & children • By doing hereditability studies of twins & adopted individuals

  4. Heredity & Temperament • Infancy • Differ in activity level, mood, heart rate responsiveness, & attention span • Born with genetically determined temperaments • Physiological dispositions to respond to the environment in certain ways • Quite stable over time

  5. Heredity & Traits • Estimate the heritability of specific traits within a group of children or adults • Favored by behavioral geneticists • An interdisciplinary field of study concerned with the genetic basis of behavior & personality • Heritability: A statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within a group.

  6. Computing Heritability • Look at adopted children • Identical v. fraternal twins • Identical twins reared apart

  7. Twins • Identical (Monozygotic) Twins: • Develop when a fertilized egg divides into 2parts that develop into separate embryos • Fraternal (Dizygotic) Twins: • Develop when two separate eggs are fertilized by different sperm • They are no more alike genetically than any other pair of siblings.

  8. Twin Studies • Studying identical twins separated near birth is one behavior genetic method • Gerald and Mark met at age 31 after being separated at birth. • Both are volunteer firefighters • Like to hunt, eat Chinese food, and watch John Wayne movies • Drink the same brand of beer, with their hands held the same way (pinky curled)

  9. Evaluating Genetic Theories • Reasons for Caution • Not all traits are equally heritable or unaffected by shared environment. • Some studies may underestimate the impact of the environment. • Even traits that are highly heritable are not rigidly fixed. • Genetic predisposition does not imply inevitability

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