Carroll’s Three-Stratum Theory of Intelligence
By the late twentieth century, intelligence research had accumulated an awkward abundance of results. Spearman had identified general covariance.
Category Theories
Clear, evidence-led guides to the major theories and models of intelligence, from psychometric structure to cognitive, developmental and network explanations.
Cattell-Horn Theory: What Are Fluid and Crystallized Intelligence?
Knowing that intelligence contains broad abilities creates a new question: **what kind of abilities are they, and why do they develop differently?
Thurstone’s Primary Mental Abilities: Is Intelligence Made of Several Abilities?
Once psychologists began taking general intelligence seriously, another problem became harder to ignore.
Spearman’s Two-Factor Theory of Intelligence: What Are g and s?
At the beginning of the twentieth century, psychologists faced an intriguing pattern. Measures that seemed to test quite different mental abilities tended to correlate.
What Is the Positive Manifold — and Why Do Intelligence Tests Correlate?
Give a large group of people a sufficiently varied set of cognitive tests: reasoning, vocabulary, memory, spatial problems, processing speed.