Biological Level of Analysis: Genetics and Behavior

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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

Transcript of Biological Level of Analysis: Genetics and Behavior

Page 1: Biological Level of Analysis: Genetics and Behavior

Biological Level of Analysis

Genetics and Behavior

Page 2: Biological Level of Analysis: Genetics and Behavior

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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)

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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?

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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