Genetic Influences – Module 5 Intro Psych Feb 22-24, 2010 Classes #14-15

Module 5: Genetic influences Module 5: Genetic influences What influences one’s behavior: Nature or Nurture? What influences one’s behavior: Nature or Nurture? The age-old debate: The age-old debate: Is it genes or is it the environment? Is it genes or is it the environment?

Principle of Genetics Master plan for your body…. Master plan for your body…. 46 chromosomes 46 chromosomes 23 chromosomes carried in the egg are paired with 23 chromosomes brought to it by the sperm 23 chromosomes carried in the egg are paired with 23 chromosomes brought to it by the sperm Each is composed of a molecule called DNA Each is composed of a molecule called DNA DNA is made up of thousands of segments which are called genes DNA is made up of thousands of segments which are called genes

Principle of Genetics Your sex is determined by the 23 rd pair – the sex chromosomes… Your sex is determined by the 23 rd pair – the sex chromosomes… From your mother always an “x” From your mother always an “x” From your father, you have a 50/50 chance of receiving an x  making you a female From your father, you have a 50/50 chance of receiving an x  making you a female From your father, you have a 50/50 chance of receiving an xy  making you a male From your father, you have a 50/50 chance of receiving an xy  making you a male XX = female XX = female XY = male XY = male

Gender Differences… The differences typically found between the sexes are small compared to the similarities… The differences typically found between the sexes are small compared to the similarities… But when it comes to casual sex… But when it comes to casual sex… See next slides… See next slides…

“I have been noticing you around campus. I find you very attractive.” Clark & Hatfield (1989) Clark & Hatfield (1989) In this study, students were approached by another student of the opposite sex, who uttered the above statement… In this study, students were approached by another student of the opposite sex, who uttered the above statement… This was followed by one of three invitations: This was followed by one of three invitations: “Would you go out tonight?” or “Would you go out tonight?” or “Would you come over to my apartment?” or “Would you come over to my apartment?” or “Would you go to bed with me?” “Would you go to bed with me?”

Go Out Go to Apt. Go to Bed Men were even more likely to say “yes” to the sexual invitation Not a single woman said “yes” to the sexual invitation About half of both sexes said “yes” to the date Percent Saying “Yes”

Variations in Perceptions and Reactions Compared to women, men perceive more sexuality in an interaction between a man and a woman Compared to women, men perceive more sexuality in an interaction between a man and a woman This is true whether they are participants or observers This is true whether they are participants or observers However, men see interactions involving their sister as platonic However, men see interactions involving their sister as platonic

Baumeister, Catanese, and Vohs (2001) Which gender has the stronger sex drive? Which desires more frequent sex? Which thinks more about sex? Which masturbates more often? Which initiates more sex? Which gender makes more sacrifices for sex?

The Burger King Study Townsend & Levy (1990) Townsend & Levy (1990) Who would you prefer: a well-dressed unattractive person or a good-looking person in a Burger King outfit??? Who would you prefer: a well-dressed unattractive person or a good-looking person in a Burger King outfit???

Burger King study: Burger King study: First, males were pre-rated into 2 groups: First, males were pre-rated into 2 groups: Handsome versus homely Handsome versus homely Each were put into 1 of 3 costumes: Each were put into 1 of 3 costumes: Armani suit with Rolex (high status), white t-shirt (medium status), or Burger King uniform (low status) Armani suit with Rolex (high status), white t-shirt (medium status), or Burger King uniform (low status) They then did the same for females They then did the same for females

Twin Studies Monozygotic Monozygotic Identical twins (one-egg) Identical twins (one-egg) Dizygotic Dizygotic Not identical (fraternal) twins Not identical (fraternal) twins Resemble one another as much as any brother or sister would Resemble one another as much as any brother or sister would

Nature or Nurture? Question: Question: Do identical twins who are adopted by separate families act like one another more than say two adopted children into the same family who have no genetic influences? Do identical twins who are adopted by separate families act like one another more than say two adopted children into the same family who have no genetic influences? Lets look at some case study research to help us determine this… Lets look at some case study research to help us determine this…

“The Jim Twins” Bouchard (1979) Bouchard (1979) Thomas Bouchard  Thomas Bouchard  University of Minnesota twin studies – extraordinary similarities between Jim Springer and Jim Lewis University of Minnesota twin studies – extraordinary similarities between Jim Springer and Jim Lewis Uncanny coincidences? Uncanny coincidences? Any limitations to this study? Any limitations to this study?

The Jim Twins Tested at the Univ of Minnesota Tested at the Univ of Minnesota Intelligence Intelligence Personality Personality Heart Rate Heart Rate Brain waves Brain waves All virtually alike as the same person tested twice All virtually alike as the same person tested twice Voice intonations and inflections were so similar that they could not tell each other’s Voice intonations and inflections were so similar that they could not tell each other’s

Twins Oskar Stohr & Jack Yufe Bouchard (1979) Bouchard (1979) Part of Bouchard’s twins study… Part of Bouchard’s twins study… Oskar Stohl and Jack Yufe were raised in environments with more obvious differences Oskar Stohl and Jack Yufe were raised in environments with more obvious differences

Did these guys share a flushing the toilet gene? Oskar raised by Grandmother in Germany as a Catholic and a Nazi Oskar raised by Grandmother in Germany as a Catholic and a Nazi Jack raised by Father in the Caribbean as a Jew Jack raised by Father in the Caribbean as a Jew Share traits and habits galore Share traits and habits galore Love spicy foods Love spicy foods Sweet liquors Sweet liquors Fall asleep in front of the TV Fall asleep in front of the TV Flush the toilet before using it Flush the toilet before using it Store rubber bands on their wrists Store rubber bands on their wrists Dip buttered toast in their coffee Dip buttered toast in their coffee Stohr is domineering toward women and yells at his wife as did Yufe before he and his wife separated Stohr is domineering toward women and yells at his wife as did Yufe before he and his wife separated

And you thought it was because you were incompatible… Is there a genetic risk of divorce? Is there a genetic risk of divorce? McGue and Lykken (1992) McGue and Lykken (1992) 1516 pairs of same-sex twins 1516 pairs of same-sex twins 722 MZ and 794 DZ 722 MZ and 794 DZ MZ > DZ MZ > DZ

McGue & Lykken (1992) Divorce Rate Study Study divorce rates among 1,500 same sex, middle-age twin pairs Study divorce rates among 1,500 same sex, middle-age twin pairs Fraternal twin who is divorced Fraternal twin who is divorced Odds of other twin divorcing go up 1.6 times (as compared to the odds of a not-divorced twin) Odds of other twin divorcing go up 1.6 times (as compared to the odds of a not-divorced twin) Identical twin who is divorced Identical twin who is divorced Odds of divorcing go up 5.5 times Odds of divorcing go up 5.5 times Estimation that people’s differing divorce risks are about 50% attributable to GENETIC FACTORS Estimation that people’s differing divorce risks are about 50% attributable to GENETIC FACTORS

Adoption Studies Adopted children are more similar to biological parents than adoptive parents Adopted children are more similar to biological parents than adoptive parents

Credits: C700/FOV D488/AP%20Psy%20Ch3.ppt?FCItemID=S02351D01&Plugin=Box#34 9,17,Sexuality Why do women’s and men’s sexuality differ? 0003C700/FOV D488/AP%20Psy%20Ch3.ppt?FCItemID=S02351D01&Plugin=Box#34 9,17,Sexuality Why do women’s and men’s sexuality differ?