- Slides: 15
Nature & Nurture in Psychology
Nature and Nurture? �Nature – genetics �Nurture – environment
Heritability � percentage of trait variation in a group/population that can be attributed to genetic differences
Heritability Suzy is timid and nonconforming Sara is very outgoing and agreeable If this pair of IDENTICAL twins is my population, what percent of their personality differences is attributed to genetic differences? Heritability is 0% Identical twins are GENETICALLY identical
Heritability Joe and Hank are not related. At birth, both were placed in identical environments that were maintained identical until they were 10 years old. At 10, Joe is withdrawn & shy. At 10, Hank is outgoing & friendly. What percentage of their personality difference is attributable to genes? Heritability is 100%
How is heritability determined? Twin Studies & Adoption Studies
Twin Studies Identical Twins Fraternal Twins same genes, same environment different genes, same environment v. Greater differences between the two groups indicate greater heritability (“nature”). ature” The trait might have a large genetic component.
Twin Studies Criticisms: (Don’t write this, just think about it) 1) Do fraternal twins really have equally similar environments to identical twins? Differences in looks or inborn temperament may cause people to treat you differently. 2) Identical twins may share a placenta but fraternal twins do not. Thus, we can’t eliminate prenatal environments as the cause of the differences between the two groups.
Twin Studies Identical Twins Raised Apart same genes, different environments Identical Twins Raised Together same genes, same environment v. Greater difference between these two groups indicates greater role of the environment (“nurture”).
Twin Studies Criticisms: (Don’t write this, just think about it) 1) Adoption agencies try to place twins in similar families so the variation in environment may be small 2) There is a very limited sample.
Adoption Studies Is the child more like adoptive parents… Adoptive Parents Nurture …or biological parents? Biological Parents Nature
Adoption Studies Note: Two related siblings that grow up in the same family are strikingly different in personality.
Nature or Nurture? � Personality � Values � Divorce � Attitudes Risk � Heart Rates � Brain Waves � Intelligence Levels � Manners Beliefs � Religious Beliefs � Involvement in charitable activities � Age of death (7% heritability) Interests (50% heritability) NATURE � Political NURTURE Intelligence Levels – separated identical twins have similar intelligence levels, BUT adopted children score higher on intelligence tests than their biological parents
How heritable is that trait? Trait Creativity Extraversion Autism Depression Sleep quality TV viewing Religious beliefs Divorce Height Population adolescents adults general 3 -5 year olds general women Heritability 25% 30 -50% 90 -95% 40 -55% 35% 10 -45% 0% 55% 92% http: //www. peele. net/lib/genes. html The Stanton Peele Addiction Website Heritability of Intelligence – most researchers believe it to be between 60 -80%
“Nature deals the hand; nurture plays the cards. ” - Charles Brewer