1. Unit 3: Biological Psychology
CHS AP Psychology
Unit 3: Biological Psychology
Essential Task 3-8:
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= Blue is R= 0 G=110 B=184
Border Grey is R=74 G=69 B=64

2. 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.

3. 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.

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

5. 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.

6. 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.

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

8. 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.

9. 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.

11. 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

12. 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

13. 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

14. Separated Twins
Critics of separated twin studies note that such similarities can be found between strangers.
However, researchers point out that differences between fraternal twins are greater than identical twins.

16. 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.

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

18. 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?

19. 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)

20. 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%

21. 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.

22. 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.

23. 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.

24. 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.

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

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

27. 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.