Intelligence is one of the most-studied constructs in all of psychology. Decades of research have established that cognitive abilities are real, measurable, and consequential — predicting academic achievement, occupational outcomes, and health across the lifespan. This hub indexes our coverage of what intelligence is, how it varies, and what shapes it.
If you want to understand the tests themselves, see the companion hub on IQ testing and psychological measurement. For modifiable lifestyle factors that affect cognitive performance, see brain health and cognitive performance.
In this hub
The g factor and the structure of intelligence
Modern intelligence research is organized around a hierarchical model: a general factor (g) sits atop broader and narrower abilities. These articles cover the foundational structure of cognitive ability.
- The g factor: what general intelligence means — the hierarchical structure of cognitive ability and what makes g general.
- Fluid vs. crystallized intelligence — the two-process distinction at the core of CHC theory.
- IQ vs. EQ: which matters more? — cognitive ability and emotional intelligence as separable predictors.
Specific cognitive domains
Below the g factor, broad abilities like working memory, processing speed, and reasoning each have distinct measurement traditions and neural correlates.
- Working memory: why it matters — the limited-capacity system at the heart of complex cognition.
- Reaction time and intelligence — processing speed as a building block of g.
- Spatial vs. abstract reasoning: one factor or two? — factor-analytic evidence on visuospatial ability.
- Cognitive measures of reasoning and language — how different batteries operationalize verbal and reasoning skills.
The neuroscience of intelligence
Brain imaging and microstructural studies have begun to identify neural correlates of cognitive ability. These articles synthesize the neuroscience of high cognitive performance.
- The neuroscience of high intelligence — what neuroimaging reveals about exceptional cognitive ability.
- White matter microstructure and cognition — how myelinated tracts support efficient information transfer.
- Neuroplasticity: how the brain rewires — the cellular and circuit-level basis of cognitive change.
Cognition, decision-making, and judgment
Cognitive ability shapes how people make decisions, evaluate evidence, and resist misinformation.
- Cognitive ability and decision-making biases — how IQ relates to susceptibility to common heuristics.
- Decision acuity and mental health — reinforcement-learning differences across psychiatric profiles.
- Eye movement models of decision making — gaze patterns as windows into cognitive process.
- Resistance to online misinformation — cognitive reflection and digital information evaluation.
- Cognitive ability and top earners — where the IQ-income relationship asymptotes.
Population trends and group differences
Mean cognitive scores have shifted across cohorts and vary across demographic groups. These articles examine the evidence carefully.
- The Flynn effect: are humans getting smarter? — a century of generational IQ change.
- Trends in the Flynn effect over time — the slowdown and reversal in recent cohorts.
- Sex differences in cognitive abilities — what the data actually show on mean and variability differences.
- Gender, education, and cognitive outcomes — how schooling moderates sex-related cognitive patterns.
- Sex differences in early education and cognition — emergence of patterns in school-age children.
Heritability, genetics, and the environment
Intelligence has both substantial genetic and substantial environmental contributions. These articles cover what twin studies, molecular genetics, and epigenetics have established.
- Heritability of intelligence: twin studies and beyond — what genes account for variation across populations.
- Epigenetics and IQ malleability — methylation, gene-environment interplay, and developmental plasticity.
- CORD7 mutation and human cognition — a single-gene window into cognitive variation.
Can intelligence be increased?
The honest answer is “sometimes, modestly, with caveats.” These articles examine the evidence on cognitive interventions across the lifespan.
- Can you actually increase your IQ? — what training, education, and environmental enrichment can and cannot do.
- How much does education raise IQ? — quasi-experimental and natural-experiment estimates.
- Growth mindset: what the meta-analyses show — the evidence on motivation-based interventions.
- Does bilingualism make you smarter? — the cognitive advantage hypothesis under scrutiny.
- Does music training increase IQ? — a critical review of the music-cognition literature.
- Intelligence and music aptitude in piano learning — how prior cognitive ability predicts skill acquisition.
- Does reading make children smarter? — reciprocal effects of literacy and cognitive growth.
- Does cannabis lower your IQ? — the evidence on cognitive effects of cannabis use.
- Cannabis and IQ decline in youth — adolescent-specific exposure effects.
- Does breastfeeding make kids smarter? — evidence vs. confounding in the breastfeeding-IQ literature.
- Maternal milk and neurodevelopment — mechanistic work on milk-borne factors and the developing brain.
Intelligence in clinical populations
Cognitive ability does not fit neatly along clinical diagnostic boundaries. These articles cover the IQ profiles of major neurodevelopmental conditions.
- Autism and IQ: intelligence in ASD — the wide range of cognitive profiles in autism spectrum.
- ADHD and intelligence: the IQ-attention link — attention’s effect on measured ability.
- Gifted children: identification and testing — high-end cognitive ability in childhood.