Biological Theory of Personality Nature v Nurture Nature

Biological Theory of Personality

Nature v. Nurture Nature! Nurture! • “They are born that way!” • Responsible for ~50% of personality • “It’s their experiences & how they were raised!” • Responsible for ~50% of personality

Biological Approach • What percentage of personality is inherited? – “Heritability” • We are not sure BUT temperaments do seem to be stable from infants to old age.

Biological Approach • Genes: units of heredity – DNA holds our chemical make-up • Affect personality because they affect our behaviors, especially on infants • Inferring the existence of relevant genes • Hope one day specific genes underlying temperaments and key traits will one day be discovered http: //www. youtube. com /watch? v=a 5 yz. RRv. ROp. E

Heritability & Temperaments • Temperaments: dispositions to respond to the environment in certain ways – Ex: reactivity, soothability, positive & negative emotionality • Studied in infants – May later form into personality traits

Heritability & Traits • Heritability: statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within a group. …what?

Heritability & Traits • Simply put, heritability is how likely a trait is transmitted from parent to child • High heritability: trait probably passed through genes • Low heritability: probably not. • Even high heritable traits can be modified by the environment.

Studies • Adoptive children – Different genes, same environment

Studies • Identical v. fraternal twins – Genetic influences would cause identical twins to be more similar than fraternal twins, despite growing up in same environment

Studies • Identical twins separated at birth – Same genes, different environments – Studies: similar personality, even though raised apart • Demonstrates heritability!

Heritable Personality Traits • • Gestures Mannerisms Moods “Big Five” traits

Practice! • I hope you have a few quiz-taking genes.

Practice! 1. What three broad lines of research support the hypothesis that personality differences are due in part to genetic differences? 2. In behavioral-genetic studies, the heritability of personality traits, including the Big Five, is typically about… a) b) c) d) 0. 50 0. 90 0. 10 to 0. 20 0

Practice! 3. A newspaper headlines announces: “Couch Potatoes Born, Not Made: Kids’ TV Habits May Be Hereditary. ” Why is this headline misleading? What other explanations of the finding are possible? What aspects of TV watching could have a hereditary component?

How’d You Do? ? 1. Research on animal personalities, human temperaments, and the heritability of traits 2. A = 0. 50 3. The headline implies there is a “TV-watching gene, ” but there obviously isn’t such a gene. The writer fails to consider other explanations. For example, perhaps some temperaments dispose people to be passive, and this disposition leads to a tendency to watch a lot of TV