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Biological Bases of Behavior

Biological Bases of Behavior. 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?

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Biological Bases of Behavior

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  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

  9. 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

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

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

  12. 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

  13. 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?

  14. 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

  15. 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? • . • . • .

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  21. 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

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

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

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