Genetics and Personality Section 3

Objectives Describe genes and explain their importance List the two scientists associated with biological perspective Evaluate personalities in animals Analyze heredity and temperament

It’s in their nature, they are born that way One daughter testy; brother good natured= so they came out of womb that way, right? Mother right? Born good natured or treating two babies differently? Nature vs. Nurture debate…again Edward Thorndike- “ the chief determining factor is heredity Kagan- detectible in infancy, remain stable in childhood % children born shy

Thorndike

Kagen= Biological

Basic information about genetics Genes- the functional units of heredity; they are composed of DNA and specify the structure of proteins Form chemical codes for the synthesis of proteins; proteins in turn affect virtually every aspect of the body Genes can effect behaviors we call “Personality” through effects on infants brain and nervous system

Puppies and Personalities Local dog park Filled out personality inventories (special project) of themselves and their dogs Found similarities of personalities Octopus Personality- attack; wait to get near; wait till nobody is looking

Heredity and temperament Temperaments Physiological dispositions to respond to the environment in certain ways Present in infancy, assumed to be innate Relatively stable over time Includes Reactivity Soothability Positive and negative emotionality chapter 2

Human Personalities First weeks of birth humans differ in activity level, mood, responsiveness, heart rate and attention span Temperaments – genetically determined; dispositions to respond to the environment in certain ways Arousal, easy to calm upset baby

Heredity and traits 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 Heritability of personality traits is about 50% Within a group of people, about 50% of the variation associated with a given trait is attributable to genetic differences among individuals in the group. Genetic predisposition is not genetic inevitability chapter 2

Heredity and traits Heritability- estimate specific traits within groups of children or adults Method favored by behavioral geneticists Scientists concerned with the genetic bases of behavior and personality traits

Hereditability

Example of heritability Entire class takes shyness test= compute scores for the group Some students close to the average, some much higher and lower than the average May estimate extent of class variation on shyness but does not explain it all Height of person= highly heritable Low= table manners ( mostly environment)

Computing Heritability Adopted children- half genes with each parent HOWEVER raised in different environment apart from birth parents OTOH share environment with adopted parents and siblings but not their genes Identical twins ( one egg divides)= shared genes Fraternal twins ( two eggs) like siblings

Evaluating genetic theory of personality A genetic predisposition does not equal genetic inevitability Today almost all psychologists who study personality regard biology and experience as interacting influences So not all genetics

Summary Gene theorists (people) Temperament Heredity Evaluations