Why This Matters
Intelligence is one of the most contested concepts in cognitive psychology, and for good reason—how we define and measure intelligence shapes everything from educational policy to hiring practices. You're being tested not just on who proposed which theory, but on the fundamental debate underlying all of them: Is intelligence one thing or many things? Does it change over time? Can it be taught? These questions drive the distinctions between theories emphasizing general cognitive ability, multiple distinct capacities, and developmental processes.
Don't just memorize names and dates. Know what problem each theorist was trying to solve and how their model differs from competing approaches. When an FRQ asks you to "compare two theories of intelligence," you need to identify whether they disagree about structure (one ability vs. many), stability (fixed vs. malleable), or scope (cognitive only vs. including social-emotional factors). Master these distinctions, and you'll be ready for any question they throw at you.
The "g" Factor Debate: One Intelligence or Many?
The oldest controversy in intelligence research centers on whether there's a single underlying mental ability that drives all cognitive performance, or whether intelligence is better understood as a collection of separate capacities. These theories use factor analysis—a statistical technique that identifies clusters of correlated abilities—to support their claims.
Spearman's Two-Factor Theory
- General intelligence (g) is the core concept—a single underlying factor that influences performance across all cognitive tasks, from math to verbal reasoning
- Specific factors (s) account for abilities unique to particular tasks, but Spearman argued these matter far less than g for predicting success
- Predictive power of g for academic and occupational outcomes remains one of the most replicated findings in psychology, making this theory foundational for standardized testing
Thurstone's Primary Mental Abilities
- Seven distinct abilities—including verbal comprehension, numerical ability, spatial relations, and perceptual speed—challenged the dominance of g
- Factor analysis supported his claim that someone could excel in spatial reasoning while being average in verbal tasks, contradicting the idea of uniform general intelligence
- Individual profiles of strengths and weaknesses became the focus, laying groundwork for later multiple intelligence theories
Compare: Spearman vs. Thurstone—both used factor analysis, but reached opposite conclusions. Spearman emphasized what cognitive tasks share (g), while Thurstone emphasized how they differ (primary abilities). If an FRQ asks about the structure of intelligence, contrast these two approaches.
Cattell-Horn-Carroll (CHC) Theory
- Hierarchical integration places g at the top, with broad abilities (second stratum) and narrow specific abilities (third stratum) below—essentially a compromise between Spearman and Thurstone
- Fluid intelligence (Gf) involves reasoning and problem-solving in novel situations, while crystallized intelligence (Gc) reflects accumulated knowledge and skills
- Most comprehensive model currently used in intelligence testing; the Woodcock-Johnson and many other modern assessments are built on CHC structure
Fluid and Crystallized Intelligence Theory
- Fluid intelligence (Gf) peaks in early adulthood and declines with age—it's your raw processing power for solving unfamiliar problems
- Crystallized intelligence (Gc) continues growing throughout life as you accumulate vocabulary, facts, and expertise from experience
- Aging implications are critical: older adults may struggle with novel problem-solving but excel at tasks drawing on accumulated knowledge
Compare: Fluid vs. crystallized intelligence illustrates that "getting smarter" and "getting slower" can happen simultaneously. This distinction explains why vocabulary scores increase with age while processing speed decreases—a common exam topic.
Beyond Cognitive Ability: Expanding What "Intelligence" Means
Some theorists argued that traditional IQ tests capture only a narrow slice of human capability. These models expand intelligence to include creativity, practical know-how, social skills, and emotional awareness—abilities that matter enormously for real-world success but don't show up on standardized tests.
Gardner's Theory of Multiple Intelligences
- Eight distinct intelligences—linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalistic—each represents a separate cognitive system
- Cultural context determines which intelligences are valued; a society that prizes musical ability will identify and nurture different "smart" people than one focused on logical-mathematical skills
- Educational applications have been enormous, though critics note the theory lacks strong empirical support from factor analysis and may conflate intelligence with talent or skill
Sternberg's Triarchic Theory of Intelligence
- Three components—analytical (academic problem-solving), creative (generating novel ideas), and practical (adapting to real-world demands)—must work together for successful intelligence
- Contextual factors matter: intelligent behavior means knowing when to adapt to your environment, when to shape it, and when to select a new one
- Balance is key—someone strong in analytical intelligence but weak in practical intelligence may ace tests but struggle to apply knowledge in everyday situations
Emotional Intelligence Theory
- Four core abilities—perceiving emotions, using emotions to facilitate thought, understanding emotions, and managing emotions—define EQ as distinct from IQ
- Malleable capacity that can be developed through training, unlike traditional views of intelligence as relatively fixed
- Predicts outcomes in leadership, relationships, and mental health that IQ alone cannot explain, though measurement remains controversial
Compare: Gardner vs. Sternberg—both reject a single g factor, but Gardner proposes independent intelligences while Sternberg emphasizes integrated components working together. Gardner's theory is broader (eight types), while Sternberg's is more focused on how intelligence operates in context.
Developmental Perspectives: How Intelligence Grows
Rather than asking "what is intelligence?" these theories ask "how does thinking develop?" They focus on processes of cognitive growth rather than measuring stable traits, emphasizing that intelligence is constructed through experience and social interaction.
Piaget's Theory of Cognitive Development
- Four sequential stages—sensorimotor (0-2), preoperational (2-7), concrete operational (7-11), and formal operational (11+)—represent qualitatively different ways of thinking
- Constructivism is the core principle: children actively build knowledge through interaction with their environment, not passive absorption of information
- Universal progression through stages occurs in the same order for all children, though timing may vary; each stage involves schemas, assimilation, and accommodation
Vygotsky's Sociocultural Theory of Cognitive Development
- Zone of Proximal Development (ZPD) defines the gap between what a learner can do alone and what they can achieve with guidance—this is where learning happens
- Social interaction drives cognitive growth; thinking is internalized social speech, and higher mental functions originate in collaborative activity
- Scaffolding—temporary support from more knowledgeable others—enables learners to accomplish tasks they couldn't manage independently
Compare: Piaget vs. Vygotsky—both are constructivists, but Piaget emphasized individual discovery while Vygotsky emphasized social guidance. Piaget saw development as driving learning; Vygotsky saw learning as driving development. This distinction frequently appears on exams.
- Computer metaphor frames the mind as a system that encodes, stores, and retrieves information through distinct stages and processes
- Attention, working memory, and long-term memory are the key components; limitations at any stage (like working memory capacity) constrain cognitive performance
- Developmental changes in processing speed, strategy use, and metacognition explain how thinking becomes more sophisticated with age
Compare: Information Processing vs. Piaget—both describe cognitive development, but Piaget proposed qualitative stage shifts while Information Processing theory emphasizes gradual quantitative improvements in speed, capacity, and strategy use.
Quick Reference Table
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| General intelligence (g factor) | Spearman's Two-Factor Theory, CHC Theory |
| Multiple distinct abilities | Thurstone's Primary Mental Abilities, Gardner's Multiple Intelligences |
| Fluid vs. crystallized distinction | Cattell-Horn-Carroll Theory, Fluid/Crystallized Theory |
| Intelligence beyond IQ | Sternberg's Triarchic Theory, Emotional Intelligence, Gardner |
| Stage-based development | Piaget's Cognitive Development |
| Social-cultural influences | Vygotsky's Sociocultural Theory |
| Cognitive processes | Information Processing Theory |
| Hierarchical models | CHC Theory (integrates g with specific abilities) |
Self-Check Questions
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Which two theories both use factor analysis but reach opposite conclusions about whether general intelligence exists? What does each emphasize?
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A 70-year-old professor has an extensive vocabulary and deep expertise in her field but struggles with novel logic puzzles. Which theory best explains this pattern, and what specific concepts apply?
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Compare and contrast Piaget's and Vygotsky's views on the relationship between development and learning. How would each theorist explain a child learning to solve math problems?
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An FRQ asks you to evaluate whether intelligence is a single ability or multiple abilities. Which three theorists would you cite for the "multiple abilities" position, and how do their models differ from each other?
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How does Sternberg's triarchic theory differ from Gardner's multiple intelligences in terms of how the components of intelligence relate to each other? Why might this distinction matter for educational practice?