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Psychology 1230: Psychology Psychology 1230: Psychology of Adolescenceof Adolescence

Don Hartmann Don Hartmann Fall 2005Fall 2005

Lecture 8b: Heredity &

Environment

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Quiz 1 InformationQuiz 1 Information80% of the multiple choice items will come 80% of the multiple choice items will come from the study guides. The MC portion of from the study guides. The MC portion of the quiz will contain the quiz will contain 30-4030-40 items from the items from the following sources:following sources:– 3-5 questions from each chapter, 3-5 questions from each chapter, – 1-2 items from each lecture, and 1-2 items from each lecture, and – 0-1 questions from each handout.0-1 questions from each handout.The essay portion will include 3-5 relatively The essay portion will include 3-5 relatively brief essay questions taken from the study brief essay questions taken from the study guides. You will have some choice over guides. You will have some choice over which questions you can choose to answerwhich questions you can choose to answer

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WEB Discussion ProcessWEB Discussion Process

GroupGroup #1#1 duedue #2 due#2 due #3 due#3 due #4 due#4 due #5 due#5 dueWhippetsWhippets 09/1209/12HottiesHotties 09/1309/134♀+1♂4♀+1♂ 09/1909/19GypsyMafiaGypsyMafia 09/2009/20JusticeLeagueJusticeLeague09/2109/21PsychedPsyched 09/2209/22PithHelmetsPithHelmets 09/2309/23MAJACSMAJACS 09/2609/26

--------------------Note: Anyone can contribute to any WEB discussion; group members are responsible to Note: Anyone can contribute to any WEB discussion; group members are responsible to

summarizing the discussion. The last day to contribute to any discussion is 3 days summarizing the discussion. The last day to contribute to any discussion is 3 days before the due date.before the due date.

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Handout SummaryHandout Summary Handout Handout WEBWEB

Date Date DateDate 14. HO-Completing a Film Review*14. HO-Completing a Film Review*08/1408/14 15. HO-Preparing a Book Review15. HO-Preparing a Book Review08/1408/14 16. Completed Class Locator16. Completed Class Locator 08/3108/31 17. Lect. #4: Introduction to Theory17. Lect. #4: Introduction to Theory09/0209/02 18. Lect. #5: Bandura18. Lect. #5: Bandura 09/0209/02 19. Supplemental Lecture: Termpaper19. Supplemental Lecture: Termpaper 09/0609/06 20. Lect. #6: Method I20. Lect. #6: Method I 09/0709/07 21. Lect. #7: Method II21. Lect. #7: Method II 09/0909/09 22. Lect. #8: Puberty22. Lect. #8: Puberty 09/1309/13 23. Lect. #8b: Heredity & Envir.23. Lect. #8b: Heredity & Envir. 09/1609/16

----------*Indicates handouts discussed in class.*Indicates handouts discussed in class.

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Supplementary ReferencesSupplementary References

Plomin, R., DeFries, J. C., Plomin, R., DeFries, J. C., McClearn, G. E., & Rutter, M. McClearn, G. E., & Rutter, M. (1997). (1997). Behavioral geneticsBehavioral genetics (3 (3rdrd ed.). New ed.). New York: W. H. Freeman.York: W. H. Freeman.

Scar, S. (1993). Biological and Scar, S. (1993). Biological and cultural diversity: The legacy of cultural diversity: The legacy of Darwin for development. Darwin for development. Child Child Development, 64Development, 64, 859-865., 859-865.

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OverviewOverviewQuestions: Questions: – Why is it difficult to assess the contributions of heredity & Why is it difficult to assess the contributions of heredity &

environment on, say, the timing of puberty?environment on, say, the timing of puberty?– What is a heritability coefficient, and why should we care?What is a heritability coefficient, and why should we care?– What are the contributions of shared & non-shared What are the contributions of shared & non-shared

environments to our behavior?environments to our behavior?– What is a GEI, and why should we care?What is a GEI, and why should we care?

Intersects with the material in our text on pp. 109-112 and Intersects with the material in our text on pp. 109-112 and 152152TopicsTopics– Heritability CoefficientsHeritability Coefficients– Shared & Non-shared EnvironmentsShared & Non-shared Environments– Genotypic-Environment InteractionsGenotypic-Environment Interactions

Next: Lecture #9 (Piaget)Next: Lecture #9 (Piaget)

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Heredity or Environment?Heredity or Environment?

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Comments on Behavioral GeneticsComments on Behavioral GeneticsDefinition: Behavioral genetics—that field that Definition: Behavioral genetics—that field that

seeks to discover the influence of heredity seeks to discover the influence of heredity and environment on and environment on individualindividual differences differences in human traits and developmentin human traits and developmentImportant methodsImportant methods– Study of pedigrees: A simplified diagram of a Study of pedigrees: A simplified diagram of a

family's genealogy that shows family members' family's genealogy that shows family members' relationships to each other and how a relationships to each other and how a particular trait or disease has been inherited.particular trait or disease has been inherited.

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More on Methods: Adoption StudiesMore on Methods: Adoption Studies– Adoption studies—e.g., the similarity of Adoption studies—e.g., the similarity of

adopted children to their adopted parents and adopted children to their adopted parents and to their biological parents.to their biological parents.

If adopted children more closely resemble their If adopted children more closely resemble their biological parents than their adopted parents, we biological parents than their adopted parents, we would conclude that the trait in question was at least would conclude that the trait in question was at least partly hereditary determined (assuming the study partly hereditary determined (assuming the study was well done)was well done)If adopted children more closely resemble their If adopted children more closely resemble their adopted parents that their biological parents, we adopted parents that their biological parents, we would conclude that the trait in question was at least would conclude that the trait in question was at least partly environmentally determined (assuming…)partly environmentally determined (assuming…)For example, in one large study, the biological For example, in one large study, the biological mother-adopted child correlation was 0.37 whereas mother-adopted child correlation was 0.37 whereas the adoptive mother-adopted child correlations was the adoptive mother-adopted child correlations was 0.22. 0.22.

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More on Methods: Twin StudiesMore on Methods: Twin Studies

– Comparisons of trait resemblence in identical Comparisons of trait resemblence in identical & fraternal twins (kinship studies).& fraternal twins (kinship studies).

For example, in studies involving more than For example, in studies involving more than 10,000 pairs of twins, the average “IQ” 10,000 pairs of twins, the average “IQ” correlations are 0.85 for identical twins and correlations are 0.85 for identical twins and 0.60 for same-sex fraternal twins. 0.60 for same-sex fraternal twins.

1111The World’s First Genetically Engineered Human Hits Adolescence: ‘We buy you the best genes in the world — for this?’ (Thinks Dad.)

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Summarizing Twin StudiesSummarizing Twin Studies

Heritability Coefficients: Heritability Coefficients: Used to estimate the degree to which Used to estimate the degree to which a characteristic is inherited, say IQ or a characteristic is inherited, say IQ or shynessshynessCompares the correlation between Compares the correlation between monosygotic twins (rmonosygotic twins (rMZMZ) and between ) and between dizygoticl twins (rdizygoticl twins (rDZDZ))If (rIf (rMZMZ) > (r) > (rDZDZ), heritability coefficient ), heritability coefficient > 0> 0

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More on the Hereditability More on the Hereditability CoefficientCoefficient

For example, For example, if the rif the rMZMZ = .85, and the r = .85, and the rDZDZ = .60, H = 2(.85-.6) = 2(.25) = .50. And = .60, H = 2(.85-.6) = 2(.25) = .50. And this value indicates at least a moderate this value indicates at least a moderate tendency for the characteristic in question tendency for the characteristic in question to be inheritedto be inheritedFor those other weirdos who like formulas, the For those other weirdos who like formulas, the formula for H is as follows (the rest of you close formula for H is as follows (the rest of you close your eyes):your eyes):H = H = 2[r2[rMZMZ – r – rDZDZ]]

Interpretation requires some important Interpretation requires some important assumptions.assumptions.

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Environments—Shared & Non-Environments—Shared & Non-sharedshared

The contribution of non-shared environments: The contribution of non-shared environments: NSE = 1 ‑ rNSE = 1 ‑ rMZMZ

Some caveats regarding shared environments Some caveats regarding shared environments (Hoffman)—as they may have anomalous effects:(Hoffman)—as they may have anomalous effects:– Can create differences as well as similarities (e.g., effect Can create differences as well as similarities (e.g., effect

of divorce on different age children)of divorce on different age children)– Non-identical twins may exaggerate differencesNon-identical twins may exaggerate differences

The effects of shared environments, obviously, The effects of shared environments, obviously, are strongest for dimension on which siblings are are strongest for dimension on which siblings are treated alike (e.g., religion)treated alike (e.g., religion)

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Genetic Determinants of Genetic Determinants of BehaviorBehavior

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Genotype/Environmental Genotype/Environmental Interactions (GEIs): 1 Interactions (GEIs): 1

Further messes our understanding Further messes our understanding of the contributions of nature and of the contributions of nature and nurture to our behavior (phenotype)nurture to our behavior (phenotype)– In certain cases, genotypes and environments In certain cases, genotypes and environments

interact in atypical manners to produce interact in atypical manners to produce phenotypes—e.g., your genotype might help phenotypes—e.g., your genotype might help determine the environment to which you are determine the environment to which you are exposed!exposed!

– As a result these GEIs make it difficult to As a result these GEIs make it difficult to distinguish genetic from environmental causesdistinguish genetic from environmental causes

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Genotype/Environmental Genotype/Environmental Interactions (GEIs): 2Interactions (GEIs): 2

Assume we wanted to apportion Assume we wanted to apportion causescauses of a of a behavior to one of two categories: Genetic (G) behavior to one of two categories: Genetic (G) and Environment (E). Where would we put the and Environment (E). Where would we put the following example in which the focus is on a kids following example in which the focus is on a kids reading speed: Cause A (reading books) was E reading speed: Cause A (reading books) was E but was caused by the child’s G (the child’s but was caused by the child’s G (the child’s hereditary predisposition to be smart). So do we hereditary predisposition to be smart). So do we put reading books in the G category or in the E put reading books in the G category or in the E category?category?

G EReading Books

? ?

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Passive G/E InteractionsPassive G/E InteractionsParents contribute to their children by providing Parents contribute to their children by providing them with genes and with an environment in them with genes and with an environment in which they can grow—and the environment which which they can grow—and the environment which they provide is dependent on the parents' genesthey provide is dependent on the parents' genesConsider EXERCISE. Parents who are genetically Consider EXERCISE. Parents who are genetically prone to exercise may provide an abundance of prone to exercise may provide an abundance of exercise equipment and encouragement. The exercise equipment and encouragement. The equipment and encouragement are clearly equipment and encouragement are clearly Environment (E), but are they at some deeper Environment (E), but are they at some deeper level? Both may be functions of the parents’ level? Both may be functions of the parents’ Genes (G), right?Genes (G), right?

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Evocative G/E InteractionsEvocative G/E InteractionsKids with different genes may evoke different Kids with different genes may evoke different reactions from their environment . E.g., reactions from their environment . E.g., smiley babies are responded to differently smiley babies are responded to differently in their social environments in their social environments than are smileless babies. So the responses than are smileless babies. So the responses of observers of the smiling child are of observers of the smiling child are environmental facilitators of the child’s environmental facilitators of the child’s increasing sociability. But the child “created” increasing sociability. But the child “created” this environment by his/her genetic this environment by his/her genetic predisposition to be smiley. So are the adults predisposition to be smiley. So are the adults who promote the child’s sociability G causes who promote the child’s sociability G causes or E causes?or E causes?

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Active G/E interactions (Niche Active G/E interactions (Niche picking)picking)

The environments The environments children choosechildren choose will be will be dependent upon their genes—will be compatible dependent upon their genes—will be compatible with their genetic predispositions.with their genetic predispositions.E.g., smart kids chose to be in intellect- E.g., smart kids chose to be in intellect- ually stimulating environments where ually stimulating environments where they become even smarter, whereas they become even smarter, whereas not‑so‑smart kids chose less intellect- not‑so‑smart kids chose less intellect- ually stimulating environments where ually stimulating environments where their intellectual growth will be decelerated. their intellectual growth will be decelerated. So do these more and less intellectually So do these more and less intellectually stimulating environments belong in the G stimulating environments belong in the G category or the E category? It is a puzzle, right?category or the E category? It is a puzzle, right?

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Summary of Puberty LectureSummary of Puberty Lecture

Heritability coefficientsHeritability coefficientsShared & Non-shared Shared & Non-shared EnvironmentsEnvironmentsGenotype- Environmental Genotype- Environmental Interactions (GEIs)Interactions (GEIs)Next: Lect. #9 (Piaget)Next: Lect. #9 (Piaget)Go in PeaceGo in Peace