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Biological Level of Analysis: Genetics and Behavior


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Section 2.2 of my IB HL Psychology text book

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Biological Level of Analysis: Genetics and Behavior

  1. 1. Biological Level of Analysis Genetics and Behavior
  2. 2. Behavioral Genetics • Behavioral genetics deal with understanding how both genetics and environment contribute to behavior • A single gene doesn’t determine complex behaviors – i.e. intelligence, criminal behavior, altruism
  3. 3. Behavioral Genetics • Individual may have a genetic predisposition towards a certain behavior – Just needs the appropriate environmental stimuli for it to manifest – Without it, the behavior won’t be developed • Diathesis-stress model: Depression results from a “genetic vulnerability” and traumatic childhood events – Doesn’t apply to everyone – Sometimes one sibling becomes depressed and the other does not
  4. 4. Inheritance • Genes and DNA is passed down to offspring • Mapping of human genes can help to explain human behavior and develop treatments – James Watson’s Human Genome Project • Role of genes in behavior is still a mystery
  5. 5. Correlational Studies • Correlational study establishes that there is a relationship between variables • No cause and effect can be determined • Genes research twins a lot to find correlations between genes and behavior – The correlation found in these studies is referred to as the concordance rate
  6. 6. Family Studies • More representative sample of the general population • Different degrees of related genetics compared to their behavior • Expected that as genetic relation increases, similarities in behavior increase also
  7. 7. Adoption Studies • Demonstrates effects of nature vs. nurture – Biology vs. environment – For example: Is the child’s IQ more similar to the IQs of the adopted parents’ or the biological parents’? • Criticisms: – Children are not representative of population – Adoption agencies tend to use selective placement to find adoptive parents who are similar to biological parents – Hard to decipher whether nature or nurture caused something
  8. 8. Intelligence • The Bell Curve by Richard J. Herrnstein • Claims: Debate about whether/how much genes and the environment have to do with ethnic differences remains unresolved • Suggests there may be intergroup differences in intelligence • Obviously controversal
  9. 9. Intelligence • Charles Spearman “g” factor – Don’t test facts and subject knowledge – Test spatial ability, reasoning, divergent thinking, and verbal fluency • Bouchand and McGue (1981) meta-analysis of 111 studies • Found that the closer the kinship, the higher the correlation for IQ
  10. 10. Minnesota Twin Study (Bouchard et al. 1990) • Identical twins raised together vs. identical twins raised apart • Concordance rates of intelligence tested • Determined 70% of intelligence can be attributed to genetic inheritance • Other 30% may be attributed to other factors
  11. 11. Minnesota Twin Study (Bouchard et al. 1990) • Pros: – Mean age was 41 years old (most twin studies are about adolescents) – Most cross-cultural study to date • Cons: – Ethical concerns in reunited twins – Equal environment assumption (just because twins lived together doesn’t mean they had the same experiences growing up) – Used media coverage to recruit participants – Frequency of contact between twins prior to study could not be controlled
  12. 12. Adoption Studies • Scarr and Weinberg (1977) & Horn et al. (1979) • Studied parents with both biological and adopted children – Same upbringing and environment, but different biology – Parents were white and middle class – Children were from lower-class with low-IQ biological parents • No significant difference in IQ correlations
  13. 13. Wahlstein (1997) • Moving an infant from a low socio-economic home to a high socio-economic home improved childhood IQ scores by 12-16 points • Suggests intelligence has a lot to do with environment • Enriched environment can raise IQ
  14. 14. Hainer et al. (1988) • PET Scan • Individuals with high IQ had a lower metabolic rate when solving a reasoning problem • No change in metabolic rate with a data recall problem • Higher IQs use less energy to think • Called the less effort hypothesis
  15. 15. Heritability in IQ Levels • Plomin and Petrill (1997) • Correlations between parents and child IQs change over time • It is possible that our genetic disposition pushes us towards environments that accentuate that disposition, thus leading to increased heritability throughout the lifespan • Socio-economic class is an important environmental factor (i.e. poverty)
  16. 16. The Flynn Effect • The Flynn Effect: the rise of average scores on intelligence tests – in most parts of the world – over the last century • Average mean scores on standard IQ tests go up by about 3 points every decade • Real increase in intelligence? Better at cracking the test? Better nutrition, schooling, childhoods, technology?
  17. 17. Darwin’s Theory of Evolution • The environment presents challenges to each individual • Those who adapt best to environment will have a greater chance of surviving and passing on genes to offspring
  18. 18. Theory of Natural Selection • Species with characteristics best suited to environment are more likely to breed • They pass on these beneficial characteristics • Explains how species acquire adaptive characteristics to survive – Or makes them more competitive in an environment • This is adaptation
  19. 19. Darwin’s Ideology • Humans have behaviors in common with other animals – Mate selection – Love of mother for offspring – Self-preservation • Evolution can be studied by looking at primates – Our closest relatives in the animal kingdom
  20. 20. Tetsuro Matsuzawa (2007) • Aim: Examine spatial memory in young chimps • Method: 3 pairs of chimps memorized numerals 1-9; had to memorize which numbers were where when replaced with blank squares • Results: Humans made many errors (especially as speed of replacement increased) Chimpanzees “showed remarkable memory” (time shown made no difference)
  21. 21. Tetsuro Matsuzawa (2007) Cont. • Chimps adapted this way to remember where food resources and dangers are • Not essential for human survival because of agriculture • Memory skills of both chimps and humans have adapted to become best suitable for the environments in which they live
  22. 22. Evolutionary Psychology • As genes mutate, those that are advantageous are passed down through natural selection • Natural selection cannot select for a behavior; only for mechanisms that produce behavior
  23. 23. Fessler (2006) • The emotion of disgust allowed our ancestors to survive long enough to produce • These offspring in turn passed the same sensitivities on to us • A pregnant woman’s immune system lowers so it doesn’t fight off the new foreign material in her womb (AKA the fetus) • Nausea response heightens to compensate for the suppressed immune system
  24. 24. Fessler (2006) Cont. • Natural selection may have helped compensate for the increased susceptibility to disease during pregnancy by increasing the urge to be picky about food • Sensitivity decreases as the risk of disease and infection decreases • Disgust = form of protection from disease
  25. 25. Curtis et al. (2004) • Aim: Test patterns in people’s disgust responses • Method: Ranked level of disgust for 20 images • Findings suggest that disgust reaction was strongest for items that threaten immune system • Higher disgust in young people • Higher disgust in women than men
  26. 26. When examining an evolutionary argument remember: • Confirmation bias (see what they expect to see) because it’s hard to test empirically • Little is known about early humans – Statements of how humans “used to be” are hypothetical • Often underestimate role of culture in shaping behavior
  27. 27. Human Genetics Research • Aims to identify particular genes involved in hereditary diseases • Participants need to know their privacy will be protected and must be fully aware of the study they are participating in • Can reveal potentially harmful information – i.e. misattributed paternity, unrevealed adoptions • Stress over possessing a gene that could link to a disease • Consent as a community should be attained