Biological Bases of Behavior

1. Biological Bases of Behavior

2. Intro • What causes our striking diversity and also our shared human nature? • How much are human differences shaped by our differing genes? • How much are human differences shaped by our environment? • Unit3C tells the complex story of how our genes (nature) and environments (nurture) define us.

3. Behavior Genetics: Predicting Individual Differences • Behavior Geneticists: study our differences and weigh the effects and interplay of heredity and environment • Jaden Agassi: tennis talent because of genes or tennis environment?

4. Behavior Genetics: Predicting Individual Differences • _______________: threadlike structures made of DNA molecules that contain genes • ______: complex molecule containing the genetic info that makes up the chromosomes • __________: small segments of giant DNA molecules, heredity

5. Genes: Our Codes for Life • Each human cell contains ___ total chromosomes • ___ donated from your mother’s egg • ___ donated from your father’s sperm • Each chromosome is paired up with a partner, and each chromosome pair contains thousands of genes, which also occur in pairs. • Sometimes a member of a pair has a louder voice, always expressing itself and masking the other, different, member of the pair…this is a dominant gene. • A recessive gene is one that is masked when the paired genes are different.

6. Behavioral Genetics • Every other human is close to being your identical twin -- _____% the same • Genome: complete instructions for making an organism • Consists of all the genetic material in that organisms chromosomes • Slight variations from common pattern give us clues to our uniqueness (why one has cancer, tall, shy) • Genotype refers to a person’s genetic makeup • Phenotype refers to the ways in which a person’s genotype is manifested in observable characteristics.

7. Identical vs. Fraternal Twins • Identical Twins: develop from a single fertilized egg that splits in two • Genetically identical(human clones) • However: • They don’t always have the same number of copies of those genes (why one may get sick) • 1 in 3 don’t share placenta (one may have more nourishment)

8. Identical vs. Fraternal Twins • Fraternal Twins: develop from separate fertilized eggs • Share fetal environment but are genetically no more similar than ordinary brothers & sisters

10. Separated Twin Studies • 2 Jim’s: woodworking, Chevy, Nascar, Miller Lite, son named James Alan (Allan), Dog named Toy, Migraines, High Blood Pressure, Chain smoking, Personality, Intelligence, Heart Rate, Brain Waves • Oskar & Jack: • One raised Catholic Nazi • One raised as a Jew in the Caribbean • Similarities: spicy food, fall asleep in front of tv, flushed toilet before using it, rubber bands wrist, dipped toast in coffee, physical attributes, attitudes, interests, fears

11. http://www.youtube.com/watch?v=Wd5Y3-F79LY

12. Separated Twin Studies • Criticisms of twin studies: • . • . • .

13. Separated Twin Studies • Criticisms of twin studies: • If any two strangers were to spend hours comparing their behaviors and life history, they would discover many coincidental similarities • People with similar economic and cultural background (like many separated twins) exhibit many similarities • Many separated twins met years before they were tested

14. Biological vs. Adoptive Relatives • Behavior geneticists also look at how: • Genetic relatives (biological parents & siblings) and environmental relatives (adoptive parents & siblings) impact development • For any trait, we can ask whether adopted children are more like: • Biological parents who contributed genes (nature) • Adoptive parents who contributed home environment (nurture) • What do you think will have a greater impact?

15. Biological vs. Adoptive Relatives • Findings: people who grow up together, whether biologically related or not, do not much resemble one another in personality • Extraversion/Agreeableness: adoptees are more similar to their biological parents • Compare to your siblings! • Environment shared by a family’s children has virtually NO discernible impact on their personalities • Link between heredity and development of personalities

16. Biological vs. Adoptive Relatives • Why are children in the same family so different? • Why does shared family environment have so little effect on children’s personalities? • . • . • .

17. Heritability • Using twin and adoption studies, behavior geneticists can mathematically estimate, the heritability of a trait • Heritability:variations among individuals that we can attribute to their differing genes • If all schools were of uniform quality, all families equally loving, and all neighborhoods equally healthy, then heritability would increase because differences due to environment would decrease

18. Heritability • If heritability of intelligence is 50% • Does that mean that your intelligence is 50% genetic? • __________ • Genetic influence explains 50% of the observed variation among people • Heritability refers to the extent to which differences among people are attributable to genes.

19. Nature vs. Nurture • Humans have enormous adaptive capacity • Person #1, barefoot = callused feet (biological adaption) • Person #2, shoes = tenderfoot • Differences obviously from ______________ • Genes & Environment work together • Genes respond to environments

20. Nature vs. Nurture • Interaction between genes and environment tell us genes are self-regulating • Genes do not lead to the same result no matter the context, genes react • Example: Butterfly that changes colors due to changes in temperature in various seasons • People with identical genes but differing experiences therefore have similar though not identical minds

21. Nature vs. Nurture • At least one known gene will, in response to major life stresses, code for a protein that controls a neurotransmitter involved in depression • By itself, the gene doesn’t cause depression • What else would be an influence? • Human differences result from bothgenetic and environmental influences

22. Gene-Environment Interaction • Interaction: interplay that occurs when the effect of one factor (environment) depends on another factor(heredity) • 1.) Environments trigger gene activity (depression) • 2.) Certain traits evoke significant responses in others (impulsive student evokes angry response from teacher) • Our genes affect how people react to and influence us = possible changes in our behavior

23. Gene-Environment Interaction • Good looks will get you that job, promotion and raise

24. Review • How have heredity and environment influenced who you are today?