Untangling Nature and Nurture Behavior Genetics: the study of the interaction of genes and environment on behavior

Heritability The percentage of trait variation in a group that can be attributed to genetic differences Depends on the population

What it IS and what it ISN’T If the heritability of “happiness” is 50% then that means that we can attribute 50% of the observed variations of happiness in the general population to genetic factors. It does NOT mean that your happiness is “50% genetic!”

Heritability Sara is very outgoing and agreeable Suzy is timid and non- conforming If this pair of IDENTICAL twins is my population, what percent of the personality differences is attributable to genetic differences between them? Thus, the heritability is 0%.

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 outgoing and friendly. At 10, Hank is withdrawn and shy. In this (very small) population, what is the heritability of their personality traits? In other words, what percentage of the difference is attributable to genes? 100%

How heritable is that trait? TraitPopulation Heritability Creativityadolescents25% Extraversionadults30-50% Autismgeneral90-95% Depressiongeneral40-55% Sleep qualitygeneral35% Religious beliefsgeneral0% Religious conservatism women40% Divorcegeneral55% Heightwomen92% The Stanton Peele Addiction Website

Twins studies and Adoption Studies I. Monozygotic vs dizygotic twins – same environment II. Monozygotic reared together vs. Monozygotic reared apart Adopted children vs biological parents and adoptive parents.

Identical Twins v.Fraternal Twins Same genes, Different genes,Same environment A great difference between the two groups would indicate greater heritability (“Nature”). The trait might appear to have a large genetic component. Twin Studies - I

Criticism: 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 - II Identical Twins Reared Together v.Identical Twins Reared ApartSame genes, Same environment Different environment Greater difference between these two groups indicates greater role of the environment (“nurture”).

Twin Studies - II Criticisms: 1)Adoption agencies try to place twins in similar families so the variation in environment may be small, and 2)There is a very limited sample.

Adoption Studies Is child more like adoptive parents… …or biological parents? Adoptive Parents - Nurture Biological Parents - Nature

Adoption Studies Note: Two related siblings that grow up in the same family are strikingly different in personality (as I’m sure many of you can attest to).

Our temperaments?

Temperament Buss and Plomin twin studies demonstrated that these elements of temperament were strongly influenced by genetics, About (50%) of the individual variation in each trait.

Heritability the extent to which differences among people are attributed to genes (not environment or other factors)

Silver Fox Experiment Silver Fox Experiment Behavioral Genetics Interdisciplinary field (psychology and biology) that studies the influence of genetic factors on behavioral traits. (Ex: Bouchard, Buss, Plomin) molecular behavior genetics: studies specific genes or teams of genes that influence behavior Epigenetics – the study of environmental influences on gene expression that occur without a DNA change (environmental triggers!!)

Evolutionary Psychology Study of the evolution of the behavior and the mind using the principle of natural selection Natural selection – principle that among the range of possible inherited trait variations, the ones that lead to increased reproduction and survival are the ones that will most likely be passed to succeeding generations –Ex: common fear of snakes, heights **** EP does NOT argue for biological determinism!!!! (the idea that biology completely dictates our behaviors) but acknowledges the role of environment

The other half? Culture – enduring traditions, ideas and attitudes, large group, transmitted to next generation Norms – rules for accepted behavior Memes – self-replicating cultural mutations (ideas or aspects of culture that spread like a virus). Ex EPIC FAIL! / TWERK / Brangelina, Kimye etc.

The genetic Revolution? If it were possible would you take a genetic test telling you what diseases you are likely to suffer later in life? If you or your spouse were pregnant, would you want the unborn child tested for genetic defects? Do you think it should be legal for employers to use genetic tests in deciding who to hire?

Heredity and Behavior Basic Principles of Genetics: - Chromosomes: Threadlike strands of DNA molecules that carry genetic information. - Genes: DNA segments that serve as the key functional units in hereditary transmission. - Homozygous Condition: 2 genes in a specific pair are the same. - Heterozygous Condition: 2 genes in a specific pair are different. *Dominant Gene: A gene is expressed over another. *Recessive Gene: A gene is masked by another. Must have a homozygous paring to manifest the recessive trait.

Punnett Square (f=father, m= mother) F1F2 M1F1 M1F2 M1 M2F1 M2F2 M2

Try these… A man with red hair (recessive) marries a woman with black hair (dominant) whose mother had red hair. What are the chances their child will have red hair? Black hair?

A man and a woman both have brown eyes but their first child had blue eyes. What are the chances that their second child will have blue eyes?

Genes: Our Codes for Life Chromosomes containing DNA (deoxyribonucleic acid) are situated in the nucleus of a cell.

Genes: Our Codes for Life Segments within DNA consist of genes that make proteins to determine our development.

Chromosomes = 1 person 23 chromosomes from mom and 23 from dad Genetic codes are in EVERY cell of your body.

Twin Biology Studying the effects of heredity and environment on two sets of twins, identical and fraternal, has come in handy.

Thomas Bouchard’s Study Studied Twins and discovered almost unbelievable similarities between adult identical twins who had been separated near birth.

Heredity + Environment = Interaction

Nature, Socialization & Gender

Gender Roles Role = prescribed / expected actions within a social position Gender roles  expectations about male / female behavior Do we (our families) fit the patterns? What happens when we deviate from the role?

Gender Identity Sense of being male or female Gender typing – acquisition of a traditional masculine or feminine role How does gender typing happen?

Social learning theory Assumes children learn by observation and imitation of others and by being rewarded or punished “Punishment” can be in the form of teasing, admonishment or other signs of disapproval. –What a good mommy you are to your dolls! –You fight / throw like a girl! –That’s not very ladylike! –Grow a pair! –Boys will be boys! –Take it like a man! –Ending up an “old maid” –Girls who climb trees “tomboys” –Sugar and spice and everything nice, that’s what little girls are made of –Snakes and snails and puppy dog tails….. –Dolls vs Action figures “Boy worlds” and “girl worlds” – despite parents attempt at not gender typing

Gender Schema Theory Schema = a concept or a lens through which something is viewed Gender becomes a lens through which a child understands her experiences Culture impresses on children what it means to be male or female  children adjust behavior accordingly W9ZgZc

Sexual Orientation Sandfort & Others, survey Bi-sexual orientation – less than 1% of respondents Most surveyed adults in 2001 reported at least 1 homosexual fantasy even if hetero in orientation

Stats – Homosexuality and the population Homosexuals usually identify with the gender that correlates with their sex though some may also be transgendered 2002 Gallup survey of US and Europe 4% of men and 2 % of women In 1970’s classified as a “Disorder” DSM of 1973 – took away designation as a mental disorder

Fraternal birth order effect Blanchard 1997, 2001 Odds of homosexuality 3% - 1 st born sons 2 nd born – 4% 3 rd born 5% and so on Why??? Possibly exposure to maternal antibodies (which intensifies each pregnancy)  failure for fetus’ brain to develop in the male- typical pattern No such effect with sibling sister birth order.

Gender Dysphoria A transgendered person does not have a disorder unless being transgendered causes distress. –Social norms and expectations re: gender expectations for males and females are often the r Replaces diagnosis of “gender identity disorder” which is no longer a “disorder” Causes of transgendered identity is still unknown

What are the realities of allowing your child to be who he / she feels she is?

My Secret Self