Unit 3: Biological Psychology AP Psychology Unit 3: Biological Psychology Module 14-1/14-2: Explain how heredity and environment work together to shape behavior with specific attention to hereditability and gene-environment interaction. Logo Green is R=8 G=138 B=76 Blue is R= 0 G=110 B=184 Border Grey is R=74 G=69 B=64

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Module 14-1/14-2: Outline Explain how heredity and environment work together to shape behavior with specific attention: Genes 101 Twins and Adoption Hereditability vs. Environmentability Strain Studies and Selection Studies Gene-environment interaction

Behavior Genetics: Predicting Individual Differences Behavior Geneticists study our differences and weigh the relative effects of heredity and environment or NATURE vs. NURTURE OBJECTIVE 2| Describe the type of questions that interest behavior geneticists.

Genes: Our Codes for Life Chromosomes containing DNA (deoxyribonucleic acid) are situated in the nucleus of a cell. OBJECTIVE 3| Define chromosome, DNA, gene, and genome, and describe their relationships.

Genes: Our Codes for Life Segments within DNA consist of genes that make proteins to determine our development.

Genome Genome is the set of complete instructions for making an organism, containing all the genes in that organism. Thus, the human genome makes us human, and the genome for drosophila makes it a common house fly.

Genes 101 Dominant Gene – Member of a gene pair that controls the appearance of a certain trait. Recessive Gene - Member of a gene pair that controls the appearance of a certain trait only if it is with another recessive gene.

Genes 101 cont’d Polygenic Inheritance – Process by which several genes interact to produce a certain trait; responsible for our most important traits.

Twin Biology Studying the effects of heredity and environment on two sets of twins, identical and fraternal, has come in handy. OBJECTIVE 4| Explain how identical and fraternal twins differ, and ways that behavior geneticists use twin studies to understand the effects of environment.

Mz vs. Dz Twins The odds of having identical twins is about 3 in 1,000, whereas the birthrate for all twins is about 32.2 in 1,000. Most (60–70%) monozygotic twins share the same placenta but have separate amniotic sacs. A small number (1-2%) of monozygotic twins share the same placenta and amniotic sac. Fraternal twins each have their own placenta and own amniotic sac.

Personality, Intelligence Separated Twins A number of studies compared identical twins raised separately from birth, or close thereafter, and found numerous similarities. Separated Twins Personality, Intelligence Abilities, Attitudes Interests, Fears Brain Waves, Heart Rate

Jim Lewis Middle Class Wife named Betty – left her love notes Son named James Alan Dog named Toy Woodworking hobby Circular white bench around a tree in his yard. Chain Smoker Bit his fingernails Drove a Chevy, watched stock car racing, and drank Miller-Lite Suffered from High Blood Pressure and Migraines

Jim Springer Calls his 37 year separated twin in February 1980 Everything down to the dog’s name is the same (except sons James Allan vs. James Alan) When played their voices, they would mistake themselves for their twin They are the first in Thomas Bouchard’s twin study Studied 80 pairs of identical twins reared apart

Let us see if they might be correct Separated Twins Critics of separated twin studies note that such similarities can be found between strangers. Let us see if they might be correct but Researchers point out that differences between fraternal twins are greater than identical twins.

Adoption Studies Adoption studies, as opposed to twin studies, suggest that adoptees (who are biologically unrelated) tend to be more different from their adoptive parents and siblings than their biological parents. OBJECTIVE 5| Cite ways that behavior geneticists use adoption studies to understand the effects of environment and heredity.

Where is the environment? Adoptees bear more resemblance in their outgoingness and agreeableness to their biological parents then to their adopted parents Two adopted children in the same home bear no more resemblance to each other than kids from two separate families.

Adoptive Studies Adoptive studies strongly point to the simple fact that biologically related children turn out to be different in a family. So investigators ask: Why are children in the same family so different? Do siblings have VASTLY 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?

Parenting Influences children’s Parenting does have an effect on biologically related and unrelated children. Parenting Influences children’s Attitudes, Values Manners, Beliefs Faith, Politics “Mom may be holding a full house while Dad has a straight flush, yet when junior gets a random half of each of their cards his poker hand may be a loser.” David Lykken (2001)

Heritability Heritability refers to the extent to which the differences among people are attributable to genes. What percentage of the difference among people’s height can be attributed to their genes? OBJECTIVE 7| Explain heritablity’s application on individuals and groups, and explain what we mean when we say genes are self-regulating. 90%

Heritability Because heritability is a proportion, its numerical value will range from 0.0 (genes do not contribute at all to phenotypic individual differences) to 1.0 (genes are the only reason for individual differences). For human behavior, almost all estimates of heritability are in the moderate range of .30 to .60.

Environmentability is the opposite It is the extent to which the differences among people are attributable to the environment. If the heritability of most human behaviors is in the range of .30 to .60, then the environmentability of most human behaviors will be in the range of .40 to .70.

What can you say? Heritability and environmentability are population concepts. They tell us nothing about an individual A heritability of .40 informs us that, on average, about 40% of the individual differences that we observe in, say, shyness may in some way be attributable to genetic individual difference. It does NOT mean that 40% of any person's shyness is due to his/her genes and the other 60% is due to his/her environment.

Animal behavior genetic studies include Strain studies Intense inbreeding over the course of many generations creates a genetically similar strain. Two or more strains are raised at once to determine the extent to which the differences among the two groups are attributable to genes (hereditability) Compare the differences

Animal behavior genetic studies include Selection Studies If a trait is closely regulated by genes then if animals with trait are interbred with those that don’t, more of their offspring should have the trait then in a normal population

Nature and Nurture Some human traits are fixed, such as having two eyes. However, most psychological traits are liable to change with environmental experience. Genes provide choices for the organism to change its form or traits when environmental variables change. Therefore, genes are pliable.

Gene-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. OBJECTIVE 8| Give and example of a genetically influenced trait that can evoke responses in others, and give another example of an environment that can trigger gene activity.

Gene-Environment Interaction Genes and environment affect our traits individually, but more important are their interactive effects. Rex Features People respond differently to Rowan Atkinson (Mr. Bean) than Orlando bloom.

Not Nature vs. Nurture Gene-Environment Interaction is Nature AND Nurture

Gene-environment correlation Passive - Bio-Parents directly pass on genes to their kids. But Bio-Parents also pass on home environments that are influenced by their own heritable characteristics. Evocative (or reactive) gene-environment correlation happens when an individual's genetic makeup evokes an environmental response. Active gene-environment correlation occurs when an individual possesses a heritable propensity to select environmental exposure. For example, individuals who are extroverted may seek out very different social environments than those who are shy and withdrawn.