Intelligence and IQ Testing: Controversy and Consensus (Chapter 9 Study Notes)

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Intelligence and IQ Testing

Definitional Confusion

Intelligence is a complex and debated concept in psychology, with no universally accepted definition. Psychologists have long struggled to agree on what constitutes intelligence.

Edwin Boring (1923) defined intelligence as "whatever intelligence tests measure," a circular definition that avoids specifying the nature of intelligence.
Key questions include: What makes some people smarter than others? Are people generally better across all tasks, or only in specific areas?

Intelligence as Sensory Capacity

Early theories, such as those by Francis Galton (1882–1911), proposed that intelligence was a byproduct of sensory capacity (e.g., hearing, vision).

Galton believed that people with better senses would acquire more knowledge.
Research did not support this theory: sensory capacities were only weakly related to each other and not related to intelligence.

Intelligence Quotient (IQ)

The concept of IQ emerged from efforts to objectively measure children's intelligence for educational placement.

Alfred Binet established that mental disability and superiority are based on the difference between chronological age and mental age.
For example, an 8-year-old with a mental age of 8 is average; with a mental age of 5 is considered mentally deficient; with a mental age of 11 is considered superior.
Binet considered children with a mental age two years below their chronological age as disabled.

Intelligence as Abstract Thinking

Modern intelligence tests, beginning with Binet and Simon (1905), focus on higher mental processes such as reasoning, understanding, and judgment.

Most theorists agree that intelligence involves abstract thinking—the capacity to understand hypothetical or theoretical concepts.
Views of intelligence differ by culture (e.g., Western vs. Eastern perspectives; wisdom and judgment vs. intellectual brilliance).
A 1921 panel of experts agreed that intelligence includes the ability to reason abstractly, adapt to novel circumstances, acquire knowledge, and benefit from experience.

General vs. Specific Abilities

Positive correlations among intelligence test items led to the theory of general intelligence (g) by Charles Spearman.

Spearman proposed that all people have a general baseline of intelligence (g), possibly related to "mental energy."
He likened g to the strength of a mental engine—some people have more powerful, efficient brains than others.

Fluid and Crystallized Intelligence

Cattell and Horn theorized that intelligence is a mix of two capacities:

Fluid intelligence: The ability to solve new problems and think logically in novel situations (e.g., solving a puzzle for the first time).
Crystallized intelligence: The accumulated knowledge and skills acquired over time (e.g., answering factual questions).

According to their model:

Fluid intelligence "flows" into crystallized intelligence as knowledge is consolidated in long-term memory.
Fluid intelligence tends to decline with age, while crystallized intelligence remains stable or may increase.

Multiple Intelligences

Some theorists, such as Howard Gardner, argue that intelligence is not a single general ability but consists of multiple distinct domains.

Gardner's "frames of mind" suggest different ways of thinking about the world.
Evidence from autistic savants supports the idea of specialized intelligences.

Intelligence Type	Characteristics of High Scores	Suggested Occupation
Linguistic	Speak and write well	Translator, editor
Logico-mathematical	Use logic and mathematical skills to solve problems	Scientist, engineer
Spatial	Think and reason about objects in three-dimensional space	Architect, artist
Musical	Perform, understand, and enjoy music	Musician, teacher
Bodily-kinesthetic	Manipulate the body in sports, dance, or other physical movements	Athlete, coach, physiotherapist
Interpersonal	Understand and interact effectively with others	Salesperson, teacher, counselor
Intrapersonal	Understand and possess insight into self	Philosopher, psychologist
Naturalistic	Recognize, identify, and understand animals, plants, and other living things	Naturalist, biologist, veterinarian

Triarchic Model of Intelligence

Robert Sternberg proposed that intelligence consists of three distinct types:

Analytical intelligence: Logical reasoning and academic problem-solving ("book smarts").
Practical intelligence: Ability to solve real-world problems ("street smarts").
Creative intelligence: Ability to generate novel and effective solutions.

Weaknesses of the model include overlap with general intelligence (g) and difficulty in proving causal relationships with job performance.

Testing Intelligence

Objective intelligence tests are necessary because self-reports are unreliable (correlations of only 0.2–0.3 with actual intelligence).

Metacognitive skills: The ability to estimate one's own cognitive abilities.
The double curse of incompetence: People with lower cognitive ability tend to overestimate their abilities.

Calculating IQ

The Stanford-Binet IQ test (developed by Lewis Terman) compares individual performance to population norms. The intelligence quotient (IQ) is calculated as:

Uses and Abuses of IQ

IQ scores are good predictors of academic achievement and are related to job performance, income, social status, and years of education.
Some argue that IQ tests may favor certain cultural groups. Culture-fair intelligence tests aim to minimize cultural bias by avoiding questions that disadvantage individuals from different backgrounds.

Eugenics Movement

IQ testing was misused in the early 20th century to justify the eugenics movement, which sought to improve genetic stock by encouraging reproduction among those with "good genes" and discouraging or preventing it among those with "bad genes." This led to unethical practices such as forced sterilization and restrictive immigration laws.

IQ Testing Today

The most widely used IQ test for adults is the Wechsler Adult Intelligence Scale (WAIS), which includes 15 subtests and generates five scores:

Overall IQ
Verbal comprehension
Perceptual reasoning
Working memory
Processing speed

Post-Secondary Admissions Tests

Tests such as the SAT, MCAT, LSAT, and GRE are designed to predict academic success in specific domains. They tend to predict first-year grades reasonably well but are less effective at predicting later academic performance.

Reliability of IQ Scores

IQ scores in adults are highly stable over time (test-retest reliability of 0.95 week to week).
IQ tests are unreliable for children under three and poor predictors of adult IQ.
Attempts to predict IQ in babies use measures like habituation and attraction to novelty.

Validity of IQ Scores

IQ scores moderately predict life outcomes such as grades (correlation ≈ 0.5) and job performance (better than interviews).
Other factors influencing success include motivation, curiosity, effort, and mental energy.

Intellectual Disability

Defined by three criteria:

Onset prior to adulthood
IQ below approximately 70
Inadequate adaptive functioning (e.g., difficulties with daily living skills)

About 1% of the North American population (mostly males) is affected. There are four levels: mild, moderate, severe, and profound. More severe intellectual disabilities are less likely to run in families.

Mental Giftedness

Top 2% of IQ scores qualify as gifted (e.g., Mensa membership).
Gifted individuals often pursue professions such as medicine, law, engineering, and academia.
Terman's longitudinal study of gifted children ("Termites") found no increased risk of burnout or mental illness.

Nature-Nurture Controversy

The twin study method is used to disentangle genetic and environmental influences on intelligence.

Greater similarity in IQ among identical (monozygotic) twins than fraternal (dizygotic) twins suggests a genetic influence.
If identical and fraternal twins from similar environments do not differ, environmental factors are implicated.

Genetic Influences on IQ

Family studies show IQ runs in families (sibling correlation ≈ 0.5; cousin correlation ≈ 0.15).
Twin studies: identical twins (0.7–0.8), fraternal twins (0.3–0.4).
Identical twins reared apart are as similar in IQ as those reared together.
Adoption studies show environmental effects but support a strong genetic component.
Severe environmental deprivation can override genetic influences.

Environmental Influences

Early intervention programs (e.g., Head Start) produce short-term IQ gains and reduce school drop-out rates.
Program effectiveness varies due to design and administration issues.
Teacher expectancy effects have a small impact on IQ.

Poverty and IQ

Jensen's cumulative deficit study found that children in poor environments show decreasing IQ scores over time.
Poor nutrition and exposure to environmental toxins (e.g., lead) are associated with lower IQs.

Flynn Effect

The Flynn Effect refers to the observed rise in average IQ scores (about 3 points per decade) over generations, likely due to environmental changes such as improved education, nutrition, and test familiarity.

Sex Differences in IQ

Few or no average differences in overall IQ between males and females.
Females tend to excel in verbal tasks and emotion recognition; males tend to perform better on spatial tasks.

Creativity

Measured by tests of divergent thinking (generating multiple solutions) and convergent thinking (finding the single best answer).
Creativity and IQ are only mildly correlated (0.2–0.3).

Emotional Intelligence (EI)

Emotional intelligence is the ability to understand and manage one's own and others' emotions, applying this understanding to everyday life.

EI is considered by some to be as important as IQ for effective functioning.
EI tests may assess self-reported emotional management or the ability to recognize emotions in others.
EI training can improve workplace coping, decision-making, and empathy.