What is intelligence (Neisser et al., 1996)?
Ability to understand complex ideas, adapt to environment, learn from experience, reason, and overcome obstacles.
What are key properties of IQ tests?
Reliable, standardized (mean=100), and predict later life outcomes.
What does predictive validity of IQ mean?
School-age IQ predicts later life achievement.
What is heritability (h²)?
Proportion of differences in a population explained by genetic variation.
Is heritability an individual measure?
No—heritability is a population statistic.
What do MZ twins share?
About 100% of DNA.
What do DZ twins share?
About 50% of DNA.
What are MZT, MZA, DZT, and DZA?
Twin study designs: MZT=MZ together, MZA=MZ apart, DZT=DZ together, DZA=DZ apart.
Simplified heritability formula?
h² = (MZT – DZT) × 2.
What did Polderman et al. (2015) find about heritability?
Heritability across traits, including intelligence, ~40–50%.
Myth I: Intelligence is inherited OR learned
Reality: Intelligence differences are partly heritable and shaped by environment.
Why is the intelligence nature/nurture debate flawed?
Both genetics and environment influence intelligence.
What is race (scientific view)?
A social, not biological, construct.
How does race classification vary?
Varies widely across cultures.
Does skin color predict genetic variation?
No—weak correlation.
Sarah Tishkoff quote meaning
Genetic tests cannot determine race; race is not a genetic category.
Do social constructs like race have real effects?
Yes—social, psychological, political consequences.
Claims made in The Bell Curve (1994)
IQ is normal, partly heritable, group differences exist and are genetic.
Main critiques of The Bell Curve
SES reduces differences; gaps declining over time; within-group heritability ≠ between-group genetic differences.
Hair colour analogy meaning
Inherited traits don’t dictate intelligence; environment can mimic genetic differences.
What is the psychological hammer?
Discrimination increases stress, affects pregnancy, alters development, with transgenerational effects.
Findings from Goosby & Heidbrink (2013)
Stress, cortisol, birth outcomes, gene expression affected by discrimination.
Public opinion on intelligence gaps (Valant & Newark, 2016)
People attribute gaps to discrimination, motivation, parenting, or genetics.
Myth II: Racial intelligence differences are genetic
Reality: Differences are environmental; racism creates biological effects.
