Twin Studies Identical Twins- twins who developed from a single fertilized egg that splits in two, creating two genetically identical organisms Called monozygotic twins

Fraternal Twins Twins who developed from separate eggs; the are genetically no more similar than other siblings, but they share a fetal environment Called dizygotic twins

Twin Studies Used to determine the heritability (characteristics that can be attributed to genetics) of a given trait Data is collected from both identical and fraternal twins on the trait Compare the data between the two groups

Twin Studies

Today’s Objectives Define nature vs. nurture issue and explain the key issues in the field of behavior genetics. Know elements of genetic code (chromosomes, DNA, & genes) Notes, video clips, journaling, pass out study guide Bell Ringer Why do you think twins separated at birth would be a great way to test the nature vs. nurture debate?

Adoption Studies Compare adopted children’s traits with those of their biological parents and adopted parents Trait similarities with biological parents: personality traits Trait similarities with the adopted parents: charitable activities Genetic Twin Studies Clip

Twin Studies: One twins study (McGue & Lykken, 1992) that looked at middle-aged twin divorce rates found that if one identical twin was divorced, then the odds of the other identical twin divorcing went up 5.5xs. However, if a fraternal twin divorced, the other fraternal twin as 1.6xs more likely to wind up divorced.

Brain Development Early experience is critical in brain development. In later life continued use is necessary to maintain neural connections in the brain.

Peer Influence Peer influence in adolescence is very powerful. Many studies suggest a peer group is correlated with school performance, smoking, and other behaviors. How much do you agree with this idea? Give me an example of peer influence?

Individualism vs. Collectivism Individualist society- focus on individual goals instead of group goals Collectivist society- individual needs are sacrificed for the good of the group. Discussion: What do you think U.S. society focuses on?

Cultural Influences In Bang Chang, Thailand, face to face conflict must be avoided at all costs, even to the point of not reporting something unpleasant. One would not say, “Your house is burning.”. Better to ask, “Why don’t you go see your house?” By leaving some food on the plate, a guest in India indicates the generosity of the host who has put so much food out that no one could eat it all. Public displays of affection between men & women in Thailand are unacceptable. However, men holding hands is considered a sign of friendship. HOW DOES THIS COMPARE TO OUR CULTURE?

Journal Reflections (to be handed in) 1. Which one do you agree with more? Nature or nurture? Why? 2. Why do you think nature versus nurture is debated? Do you think it is possible to answer this question definitively? Why or why not? 3. What effect might finding the answer to the nature/ nurture debate have on our society? 4. If you were raising identical twins, what might you do to make sure that they were unique individuals? Explain your answer. 5. Based on what you have learned, do you think it is possible for people to change? Why or why not? 6. If you are not a twin, would you rather be an identical or a fraternal twin? Why? What do you think would be some of the challenges of being a twin? If you are a twin, write a couple of sentences about the experience. Is it fun? Difficult? If you have other siblings, is your relationship with your twin different from the relationship with your other siblings? If so, what makes it different?

Today’s Objectives Define nature vs. nurture issue and explain the key issues in the field of behavior genetics. Know elements of genetic code (chromosomes, DNA, & genes) Discussion, notes, video clip, journal reflections