LECTURE 11: Intelligence Testing: Measurement, Types, and Influences

Intelligence Testing

Measuring Intelligence

Intelligence is a complex psychological construct that researchers attempt to measure using standardized tests. The measurement of intelligence has evolved over time, with various approaches and tools developed to assess cognitive abilities.

• Intelligence as a Construct: In psychology, constructs are theoretical concepts inferred from observable behavior. Intelligence is operationalized through tests, but the way it is measured, interpreted, and used can have significant consequences (e.g., historical misuse in eugenics).

• Approaches to Testing:

  • Anthropometric Approach (Galton): Early methods focused on measuring physical and mental variation, such as sensory tests.

  • Stanford-Binet Test: Assesses the ability to think, understand, reason, and adapt. Includes tasks of varying difficulty to determine mental age and intelligence quotient (IQ).

  • Deviation IQ: IQ scores are standardized so that the average is 100, with scores distributed normally across the population.

• Wechsler Adult Intelligence Scale (WAIS):

  • Measures general ability index (GAI) and cognitive proficiency index (CPI).

  • Includes subtests for verbal comprehension, perceptual reasoning, working memory, and processing speed.

Example: The normal distribution of IQ scores shows that most people score near the average, with fewer individuals at the extremes.

Problems with Testing

Intelligence testing faces several challenges, including cultural and linguistic bias, historical misuse, and psychological effects on test-takers.

• Bias: Tests may be biased due to language or cultural differences (e.g., Rey Complex Figure test).

• Eugenics and Racial Superiority: Intelligence tests have been misused to justify discriminatory practices and policies.

• Stereotype Threat: Awareness of stereotypes can affect performance due to increased physiological arousal and focus on self-performance.

Example: Historical documents and quotes illustrate the misuse of intelligence testing in eugenics and segregation.

Types of Intelligence

Intelligence as a Single Ability

Some theories propose that intelligence is a general ability underlying all cognitive tasks.

• Spearman's g: The general intelligence factor (g) represents "mental energy" and is correlated with school performance, work, and neural processing.

Intelligence as Multiple Abilities

Other theories suggest intelligence consists of multiple, distinct abilities.

• Spearman's Two-Factor Theory: Intelligence includes both general (g) and specific (s) skill-based abilities.

• Thurstone's Seven Factors: Word fluency, verbal comprehension, numeric ability, spatial visualization, memory, perceptual speed, reasoning.

• Hierarchical Models: Combine general and specific abilities.

• Fluid vs. Crystallized Intelligence:

  • Fluid Intelligence (Gf): Ability to solve novel problems (e.g., Raven's Progressive Matrices).

  • Crystallized Intelligence (Gc): Accumulated knowledge and skills.

• Gardner's Theory of Multiple Intelligences: Proposes several independent intelligences, including linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, naturalist, and existential.

Example: Raven's Progressive Matrices assess fluid intelligence through pattern recognition and logical reasoning.

Do People Have Individualized Learning Styles?

The concept of individualized learning styles (e.g., visual, auditory, kinesthetic) is popular but not strongly supported by research. Encoding style and interest are more important than modality.

• Key Point: There is little evidence that teaching to a preferred learning style improves outcomes.

Influences on Intelligence

Biological Factors

Genetic and biological factors play a significant role in individual differences in intelligence.

• Heritability: The proportion of variance in intelligence attributable to genetic factors.

• Behavioral Genomics: Studies how genes influence cognitive abilities.

• Gene Knockout Studies: Experimental removal of specific genes to study their effects on intelligence.

Relationship	Genetic Relatedness	IQ Correlation
Identical twins (reared together)	1.0	~0.85
Fraternal twins	0.5	~0.60
Siblings	0.5	~0.45
Unrelated individuals	0	~0.00
Additional info:	Heritability estimates vary by age and environment.

Environmental Factors

Environmental influences also affect intelligence, including family, education, and socioeconomic status.

• Birth Order: May influence cognitive development.

• Socioeconomic Status: Access to resources and stimulation can impact intellectual growth.

• Nutrition: Adequate nutrition is essential for brain development.

• Nootropics: Substances that may enhance cognitive function.

• Education: Staying in school and engaging in learning activities supports intellectual development.

Example: Studies show that children from enriched environments tend to score higher on intelligence tests.

Summary Table: Major Theories and Factors in Intelligence

Theory/Factor	Description	Key Example
Spearman's g	General intelligence factor	IQ tests
Thurstone's Factors	Multiple cognitive abilities	Verbal, numeric, spatial
Gardner's Multiple Intelligences	Distinct types of intelligence	Musical, interpersonal
Fluid/Crystallized Intelligence	Problem-solving vs. acquired knowledge	Raven's Matrices
Biological Factors	Genetics, heritability	Twin studies
Environmental Factors	Socioeconomic, education	Schooling effects

Key Equations

• IQ Calculation (Stanford-Binet): $IQ = \frac{\text{Mental Age}}{\text{Chronological Age}} \times 100$

• Deviation IQ: $IQ = \frac{\text{Individual Score} - \text{Mean Score}}{\text{Standard Deviation}} \times 15 + 100$

Additional info: These equations standardize intelligence scores for comparison across populations.