3Behavior Genetics and Evolutionary Psychology Module 8
4Behavior Genetics: Predicting Individual Differences Genes: Our Codes for LifeTwin and Adoption StudiesTemperament, Heredity, and PersonalityGene-Environment Interaction
5Evolutionary Psychology: Understanding Human Nature Natural Selection and AdaptationEvolutionary Success Helps Explain SimilaritiesAn Evolutionary Explanation of Human SexualityTHINKING CRITICALLY ABOUT: The Evolutionary Perspective on Human Sexuality
6Behavior Genetics: Predicting Individual Differences Behavior Geneticists study our differences and weigh the relative effects of heredity and environment.Environment is every nongenetic influence.
7Genes: Our Codes for Life Chromosomes are threadlike structures that contain DNA (deoxyribonucleic acid), a complex molecule containing genetic information.Preview Question 1: Our genes predispose our biology. Does this mean they determine our behavior?
8Genes: Our Codes for Life Genes are the biochemical units of heredity that make up chromosomes. They are segments of DNA capable of synthesizing a protein.Gene
9Twin and Adoption Studies Studying the effects of heredity and environment on both identical (monozygotic) twins, which develop from one egg, and fraternal (dizygotic) twins, which develop from two separate eggs, is useful in studying genetics.Preview Question 2: How do twin and adoption studies help us understand the relative influence of environment and heredity?
10Personality, Intelligence Separated TwinsA number of studies compared identical twins reared separately from birth, or close thereafter, and found numerous similarities.Separated TwinsPersonality, IntelligenceAbilities, AttitudesInterests, FearsBrain Waves, Heart Rate
11Separated TwinsCritics of separated twin studies note that such similarities can be found between strangers. Researchers point out that differences between fraternal twins are greater than identical twins.
12Biological Versus Adoptive Relatives Adoption studies, as opposed to twin studies, suggest that adoptees (who may be biologically unrelated) tend to be different from their adoptive parents and siblings.
13Adoptive StudiesAdoptive studies strongly point to the simple fact that biologically related children turn out to be different in a family. So investigators ask:Do siblings have differing experiences?Do siblings, despite sharing half of their genes, have different combinations of the other half of their genes?Ultimate question: Does parenting have an effect?
14Parenting Influences Children’s Parenting does have an effect on biologically related and unrelated children.Parenting Influences Children’sAttitudes, ValuesManners, BeliefsFaith, Politics
15Temperament and Heredity Temperament refers to a person’s stable emotional reactivity and intensity. Identical twins express similar temperaments, suggesting heredity predisposes temperament.Preview Question 3: What is the relationship between temperament and personality?
16Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity.A genetic predisposition that makes a child restless and hyperactive evokes an angry response from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression.Preview Question 4: How do genes and environments interact?
17Gene-Environment Interaction Both genes and environment affect our traits, but the interaction, the interplay that occurs when the effect of one depends on another, is most important.People respond differently toWill Ferrell than to Zac Efron.
18Evolutionary Psychology: Understanding Human Nature Evolutionary psychology studies why we as humans are alike. In particular, it studies the evolution of behavior and mind using principles of natural selection.Natural selection is an evolutionary process through which adaptive traits are passed on to ongoing generations because these traits help animals survive and reproduce.Preview Question 5: How do evolutionary psychologists use natural selection to explain behavior tendencies?
19Natural Selection and Adaption Through artificial selection, biologists like Belyaev and Trut (1999) were able to artificially rear and domesticate wild foxes, selecting them for friendly traits.L.N. Trur, American Scientist (1999) 87:Any trait that is favored naturally or artificiallyspreads to future generations.
20Natural Selection and Adaption Does natural selection explain our human tendencies?Nature has selectedadvantageous variations from among gene combinations and mutations (random errors in gene replication).But our genetic traits are not as hardwired as those of animals and so genes and experience shape our lives, allowing us to adapt and learn.
21Evolutionary Psychology Today Evolutionary psychologists have addressed questions such as these.Why do infants fear strangers when they become mobile?Why do people fear spiders and snakes and not electricity and guns?How are men and women alike? How and why do men’s and women’s sexuality differ?
22An Evolutionary Explanation of Human Sexuality Gender Differences in SexualityMales and females, to a large extent, behave and think similarly. Differences in sexes arise in regards to reproductive behaviors.Question (summarized)MaleFemaleCasual sex58%34%Sex for affection25%48%Think about sex everyday54%19%Preview Question 6: How might and evolutionary psychologist explain gender differences in mating preferences?
23Natural Selection & Mating Preferences Natural selection has caused males to send their genes into the future by mating with multiple females since males have lower costs involved.However, females select one mature and caring male because of the higher costs involved with pregnancy and nursing.
24Mating PreferencesMales look for youthful appearing females in order to pass their genes into the future. Females, on the other hand, look for maturity, dominance, affluence and boldness in males.Data based on 37 cultures.
25Critiquing the Evolutionary Perspective - Evolutionary psychologists take a behavior and work backward to explain it in terms of natural selection.- Evolutionary psychology proposes genetic determinism and undercuts morality in establishing society.- Where genders are unequal, gender preferences are wide, but when they are closely equal, preferences narrow down.Preview Question 7: What are the key criticisms of the evolutionary perspective on human sexualiy?