The Nature and Nurture of Behavior

1. The Nature and Nurture of Behavior

2. Let’s start with genetics . . . • Gene • A stretch of DNA that produces a specific protein, which in turn forms building blocks of our bodies or drives the processes that allow us to live • DNA (deoxyribonucleic acid): molecule that contains genes • Human instruction manual: genes affect physical features, such as eye color and height, and behavior • Dogs are bred for genetic disposition/behavior • One gene in fruit flies can be altered to produce courtship behavior between two males

3. Genetics: Tour the Basics • Go to: • http://learn.genetics.utah.edu/ • Tour: “The Basics and Beyond”

4. The Human Genome Project • Genome: the complete instructions for making an organism • Project ran from 1990-2003 (completed 2 years ahead of schedule • http://www.ornl.gov/sci/techresources/Human_Genome/project/ • What are some of the social and ethical implications for genetic screening?

5. Darwin’s Natural Selection • Key is genetic fit with environment • Mutation • Depending on environment, genetic makeup or organisms evolves throughout generations of offspring, producing changes in the dominant physical features and behavior of a group of organisms

6. Evolutionary Psychology • Using principles of natural selection, focuses on the evolution of behavior and the mind • Evolutionary psychologists study how natural selection favoured behavioural tendencies in order to explain commonalities in language learning, attention, perception, memory, sexual behaviour, reasoning and more.

7. Evolutionary Psychology • All organisms including humans are “gene-producing machines” with the basic motivation of perpetuating their own genetic pool. • Our genes predispose us to act in ways that enhance chances of surviving and spreading’ this motive underlies are behaviour

8. Evolutionary Psychology • Critics: • Evolutionary psychologists make to many hindsight explanations • They underestimate the role of culture

9. Evolutionary Theory: The Misunderstandings • Genetic Determinism – the idea that only genes control behaviour. In fact, human behaviour cannot occur without: • Evolved adaptations • Environmental influences

10. Evolutionary Theory: The Misunderstandings • That adaptive mechanisms are “optimally designed” – evolutionary psychologists recognize that the environment keeps changing, but evolution occurs slowly (humans are better designed for earlier environments)

11. Evolutionary Psychology • Mating behaviors • One of the most studied areas in evolutionary psychology • Why do we find certain characteristics attractive in a potential mate?

12. Sexuality • Task: • Write down 5 or 6 attributes that you look for in a mate • Handout 3-3 • Comparison of Characteristics

13. Evolutionary Psychology – Gender Differences in Attraction • Women prefer economic resources & older partners • Men prefer physical attractiveness & younger partners • These differences may arise from the different social roles the genders have historically held or because of evolutionary factors • These differences are more typically seen in cultures with gender inequalities

14. The Coolidge Effect • What is it? • What would be the evolutionary explanation for the Coolidge effect?

15. Behavioral Genetics • Researches in this field study the contribution of heredity to individual differences in personality, mental ability, and other human characteristics • How much of the differences among people are due to their genes and how much are due to the environment? • Genes cannot be described in isolation: they can only be characterized in relation to the environments in which they operate

16. Nature vs. Nurture • No one argues in terms of nature or nurture today, but rather scientists understand that heredity and environment interact to produce not only our psychological traits but even our most physical traits (i.e. body weight)

17. Nature-Nurture: Body Weight • Previous belief: emotional disturbance, heaviness caused by over-eating • Now: set-point (the weight you stay at when you are not trying to gain or lose) • In U.S., half of adult population is overweight – obesity genes have not changed that fast.

18. Twin Studies • Identical twins: same egg, same genes, thus they develop from a single fertilized egg. May have separate placentas. • Zygote splits (monozygotic) • Fraternal twins: different eggs, different genes, thus they develop from two fertilized eggs. They have separate placentas. Genetically no more similar than siblings. • Two separate zygotes (dizygotic)

19. Identical Twins • More similar than fraternal twins in: • Abilities • Personality traits • Interests • Emotional stability • Attitudes towards reading • Playing sports • Assisted suicide • Divorce (5.5 times more likely compared to 1.6)

20. Identical Twins • Identical twins reported being treated alike. So is it experience or genes that are accounting for their similarities?

21. Separated Twins • More alike than fraternal twins raised together (MTS). • Identical twins share the same womb (that’s environmental) and crucial to brain development. While the IQ’s of identical twins are more similar, the IQ’s of fraternal twins are more similar than siblings even though they are genetically no more similar.

22. Adoption Studies • Why are children in the same family so different? • Genes? • Peer influence? • Birth order? • Life events? • Adoption studies • Compared adopted kids with biological and adopted parents

23. Adoption Studies • Findings? • People who grow up together, whether biologically related to not, do not much resemble each other in personality • Adopted children have traits more like there biological parents than there adoptive parents

24. Adoption Studies • So does adoptive parenting matter? • Attitudes, values , manners, faith, politics as identical as identical twins. • In adoptive homes, less neglect, abuse, divorce. • They score higher than biological parents on IQ tests. • Fewer problems than the children of mothers who changed their mind about adoption.

25. Temperament Studies • Examining how emotionally excitable an infant is • ‘Easy’ babies are cheerful, relaxed & predictable • ‘Difficult’ babies are more irritable, intense & unpredictable • Temperament is mostly stable and mostly based on heredity • Earlier temperament predicts later temperament and behavior • Identical twins have more similar temperaments than fraternal twins

26. Assignment • Handout 3-5 • Find someone you don’t know at lunch today and complete the questionnaire. • Be prepared to discuss your findings.

27. Nature vs. nurture? • The environment has very little effect on personality development • But that doesn’t mean that your parents don’t effect you at all • Their influence can be seen in your attitudes, values, manners, religion, and politics • Most behaviors/traits are an interaction of your genes and the environment

28. Environmental Influence • Should we really blame the parents? • NO in the environmental sense and YES in the genetic sense • Experience and brain development • Use it or lose it, especially early on • Peer influence • Parents are necessary for early childhood survival – peers are necessary for lifelong survival • Peers are who we play with, work with, and eventually mate with

29. Environmental Influence Genetic differences account for about half of our person-person differences in personality. What accounts for the rest? Parental nurture? Prenatal nutrition? Early stimulation? Peer influences? Culture?

30. Parental Influence • Recall, shared environmental influences account for less than 10% of children’s personality differences • What matters is how parents respond to a child’s genetically influenced characteristics (the “relationship-code” as termed by Reiss). • The aggressive, fearless and impulsive boy (criminal or astronaut?)

31. Parental Influence • Recall, shared environmental influences account for less than 10% of children’s personality differences • What matters is how parents respond to a child’s genetically influenced characteristics (the “relationship-code” as termed by Reiss). • The aggressive, fearless and impulsive boy (criminal or astronaut?)

32. Pre-natal Influence • Embryos receive different nutrition and varying exposure to toxic agents • Shared placentas (2/3 of identical twins) do not translate into equal blood supply. One twin can be “greedy” or be better positioned. • Early research is indicated that twins in separate placentas are less similar than twins in the same placenta

33. Experience & Brain Development • Studies with rats in impoverished environments. • Studies with string musicians show larger and more complex neurons. • Critical period for learning language.

34. What has been the most important influence in your life?

35. Peer Influence • As the child ages, parental influence decreases and peer influence takes over. • Preschoolers will eat food with friends they don’t eat at home • Immigrant children lose parent culture if placed with a peer group of nonimmigrants • Teens who smoke have friends who smoke • Selection Effect: we seek out peers with similar attitudes and interests

36. Peer Influence Check out: http://home.att.net/~xchar/tna/ For information on peer influence

37. Cultural Influence • Culture • The behaviors, ideas, attitudes, and traditions shared by a large group of people • Norms: the rules for accepted and expected behavior (based on group membership) • Regardless of the cultural norms of a group, most are very successful at raising children • One important consideration is that while there are significant cultural differences present, we are still more alike than we are different

38. Gender – Biologically Speaking • Until the 7th week of pregnancy, all babies are female • It’s the activation of testosterone in a fetus that has the XY pair of chromosomes that triggers male organ production • In the fourth & fifth months, different brain patterns develop due to different levels of testosterone and ovarian hormones

39. Gender – Socially Speaking • Gender roles • The expectations about how men and women behave • In nomadic cultures, there is minimal gender role occurrence • Boys and girls experience the same upbringing • In agricultural societies (of which ours originated), there are strict gender role structures in place • Most of our gender identity is acquired through social learning

40. Gender Roles • What pressure (if any) do you feel to conform to gender roles?

41. Conclusion • “To what extent to biology and society determine gender roles?” • Make some point form notes on the following video to discuss next class (watching this video at school is best). • Go to the Annenberg site on the blogand watch “#17 Sex and Gender” or “youtube” it.