Unit 14: Intelligence and Its Measurement
What a single IQ score is trying to capture, why it keeps rising across generations, and how a test can distort the very performance it measures.
4 topics · 14 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
What It Means to Measure Intelligence
- How it worksHow does a general intelligence factor, g, emerge from the fact that scores on different mental tests all correlate with each other?
- Common mistakeWhy isn't intelligence fully captured by a single number on a single test?
- Going furtherWhat happens to the correlation between different mental abilities when you test a much more narrowly selected group, like only Harvard students?
Your turn1 of 2
Scores on two different mental ability tests correlate at 0.598. Find r squared, the percent of shared variance between them, part of the evidence used for a general intelligence factor g.IQ Tests and Standardization
- How it worksHow does standardizing a test on a large sample turn a raw score into a comparable IQ number centered at 100?
- Worked exampleFind why the Flynn effect, a rise of about 3 IQ points per decade, forces test makers to keep re-standardizing IQ tests.
- Common mistakeWhy isn't a rising average IQ score proof that each new generation is innately smarter than the last?
Your turn1 of 2
The Flynn effect raises average IQ scores by about 3 points per decade. Find how many points average IQ would be expected to rise over 43 years at this rate.The Heritability of Intelligence
- How it worksHow do twin and adoption studies estimate that adult IQ is substantially, but far from entirely, heritable?
- Worked exampleFind what a heritability estimate of 0.6 for adult IQ does, and does not, tell you about any one individual's intelligence.
- Common mistakeWhy doesn't a highly heritable trait mean group differences in that trait must be genetic too?
Your turn1 of 2
Adult IQ has a heritability of about 0.644 within a given population. Find the percent of variance in IQ attributable to environmental and other non-genetic factors within that same population.Stereotype Threat
- How it worksHow does the anxiety of confirming a negative stereotype about your group use up mental resources needed for the test itself?
- Worked exampleFind why women told a math test showed no gender differences performed equally to men, while women given no such reassurance scored lower.
- Common mistakeWhy isn't a test-score gap tied to stereotype threat proof of a real underlying ability gap?
- Going furtherWhat happens to a performance gap between two groups when the same test is reframed as not measuring the stereotyped ability at all?
- Ties togetherHow does stereotype threat connect back to the limits of introspection, since the anxious thoughts driving it often go unnoticed?
Your turn1 of 2
Men in a study score 81 points on average on a math test. Women given no reassurance about gender fairness score 66 points on average, a gap attributed to stereotype threat. When told the test shows no gender differences, women's scores rise to fully match men's. Find the size of the stereotype-threat-attributable gap.