PS102 Lecture Notes - Lecture 16: Fluid And Crystallized Intelligence, Twin Study, Behavioural Genetics
Nature vs Nurture
● Behavioural genetics: a field of research that investigates the relative effects of
heredity (nature) and environment (nurture) on behaviour and ability
Genetics and IQ
● Twin studies - identical = one egg, fraternal = two eggs
● Removes variability from environment
● Correlation between identicals IQs are about .86, for fraternals about .60
● Even when identicals are reared apart, the correlation is about .75
● Suggests that genetics does play some role in IQ
● Identicals high, fraternals moderate, siblings that aren’t twins are low
● Heritability ratio: an index of the degree to which a trait is due to heredity/genetics
● Population based statistic (not individual)
● Range for IQ is about .4 to .7
Environment and IQ
● Environment also plays a role in IQ
● Evidence: impoverished environments
○ The longer a child is in an impoverished environment, the lower the IQ
● Enriched environments - can improve IQ
○ Eg illinois, rural, isolated community, once became mainstream IQ increased by
10 points
○ Adoption studies, some gains if children adopted early
● Flynn effect: environmental effects, such as industrialization and enrichment, have
resulted in an increase in IQ scores
○ About 3-5 or more IQ points per decade (some parts of world show greater gains
than others) - more for fluid that crystallized intelligence
Controversies and IQ
● Between group differences - are they possible?
○ SES (talked about impoverished environments)
○ Race/ethnicity
Culture-Fair Testing
● Are IQ tests culturally laden?
○ Argue that tests are designed to assess abilities of specific groups (no dialects,
experiences of western mainstream society)
○ Eg vocabulary items (traditional WISC-spade, vs. shovel)
● Construct culture fair/culture free tests - raven's matrices
Emotional Intelligence
● Capabilities - necessary for success in life
○ Workplace, intimate personal relations, social interactions
○ It is unrelated to IQ scores
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Document Summary
Behavioural genetics: a field of research that investigates the relative effects of heredity (nature) and environment (nurture) on behaviour and ability. Twin studies - identical = one egg, fraternal = two eggs. Correlation between identicals iqs are about . 86, for fraternals about . 60. Even when identicals are reared apart, the correlation is about . 75. Suggests that genetics does play some role in iq. Heritability ratio: an index of the degree to which a trait is due to heredity/genetics. Range for iq is about . 4 to . 7. Identicals high, fraternals moderate, siblings that aren"t twins are low. Environment also plays a role in iq. The longer a child is in an impoverished environment, the lower the iq. Eg illinois, rural, isolated community, once became mainstream iq increased by. Adoption studies, some gains if children adopted early. Flynn effect: environmental effects, such as industrialization and enrichment, have resulted in an increase in iq scores.
