intelligence and testing

Psychological Measurement and Intelligence

Introduction to Intelligence Testing

  • Definition of Intelligence: Psychological measurement conceptualizes intelligence as a mental capacity. This is analyzed through performance on various mental tests.

  • Historical Context:

    • Marilyn vos Savant: Achieved a mental age corresponding to an individual aged 23 at age 10, with an IQ of 228 (highest on Stanford-Binet), and deviation IQ score of 190 (recognized by Guinness).

    • Technological Reference: Discussion of the Jarvik 7 artificial heart may imply comparisons to mental functions and capacities.

Historical Figures in Intelligence Testing

  • Alfred Binet: Introduced the concept of "mental age."

  • William Stern: Coined the term “IQ.”

  • Lewis Terman: Developed the 1916 Stanford-Binet Test, focusing on the relationship between mental age (MA) and chronological age (CA). The formula for IQ is:
    IQ = \frac{MA}{CA} \times 100

  • Current Deviation IQ:

    • Mean score is standardized to 100, with half of the population above and half below.

    • Standard deviation is set to 15, contributing to a bell curve distribution in IQ scores.

    • SAT scores share a similar distribution with a mean of 500.

Developmental Intellectual Disability

  • Definition: Characterized by deficits in general mental abilities (IQ ≤ 70) and impaired adaptive functioning in daily life, commencing before adulthood (ages less than 18).

  • Prevalence: Approximately 85% of those with developmental disabilities have mild intellectual disabilities. Such individuals can often be mainstreamed; adults may work and live more independently.

  • Severe Cases: A significantly lower intellectual ability is defined as 2 standard deviations below the mean (IQ < 70).

  • Historical Terminology:

    • Moron: IQ between 55–75 (mild)

    • Imbecile: IQ between 35–55 (moderate)

    • Idiot: IQ between 20-40 (severe or profound, below 25)

  • Ethical Implications: The term “retarded” is considered pejorative and analogous to other socially derogatory expressions. There’s a call for educated individuals to discourage such terminology.

  • Gifted: Identified as those with IQ above 130, or “genius” levels of IQ are considered above 145.

  • Environmental Impact: Historical lead exposure has reportedly reduced the expected number of individuals with IQs above 130.

  • Genetics vs. Environment: Approximately equal contributions of genetics and environment to intelligence, noting that individual brain development is influenced by environmental interactions. Examples include comparisons of wild-type rats in enriched versus stressed environments.

  • Higher Ability Definition: Significantly higher intellectual achievement is defined as 2 standard deviations above the mean (IQ > 130).

Theories of Intelligence

  • Sternberg’s Triarchic Theory:

    • Proposes three distinct types of intelligence: analytic, creative, and practical.

  • Spearman’s Two-Factor Theory:

    • Proposes a general intelligence factor (g) and a specific intelligence factor (s).

    • Fluid Intelligence: The innate ability to solve problems, reason, and remember, which is genetically-influenced.

    • Crystallized Intelligence: The knowledge gained from experiences, including education and culture, and is not innate.

  • Cattell’s Perspective: Further distinguishes between fluid and crystallized intelligence, aligning with Spearman’s framework.

Multiple Intelligences Theory

  • Howard Gardner’s Theory (1983):

    • Suggestion of multiple types of intelligence: linguistic, logical-mathematical, musical, bodily-kinesthetic, spatial, interpersonal, intrapersonal, and naturalistic.

    • Gardner later expressed regret over using the term "intelligence," suggesting that "abilities" or "gifts" may be more appropriate.

Test Characteristics in Psychological Measurement

  • Reliability: Refers to the consistency of test results upon retesting.

  • Validity: Measurement of whether a test assesses what it claims to measure, which includes:

    • Construct Validity: Captures the intended construct or trait.

    • Content Validity: Covers a broad range of relevant elements.

    • Criterion Validity: Ability to predict performance.

  • Standardization: Enables comparisons across different individuals and demographics.

    • Involves calculating the mean (average score) and standard deviation (measure of spread).

  • Types of Tests:

    • Intelligence Tests: Assess mental capabilities (e.g., Wechsler, Stanford-Binet, WISC-IV).

    • Achievement Tests: Measure acquired information or skills (e.g., classroom exams, driver’s license tests).

    • Aptitude Tests: Forecast potential learning rates (e.g., SAT, renamed Scholastic Assessment Test).

IQ Controversy: Measurement Considerations

  • Significant discussions surrounding what IQ tests fundamentally measure: intelligence alone or a combination of intelligence and other contributing factors.

  • Distribution: Concepts related to normal distribution (bell curve) and its application to IQ scores and characteristics.

Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV)

  • Assessment Focus: Measures intellectual abilities specifically in children through various subscales.

  • Cultural Fairness: Emphasizes the need for culture-fair tests, such as Raven’s Progressive Matrices Test, evaluating different cognitive abilities.

The Impact of Cultural Beliefs on Intelligence

  • Recognition of cultural beliefs that influence perceptions of education versus inherent ability, which subsequently affect academic success.

  • Factors Influencing Variation in Intellectual Ability:

    • Genetic dispositions and innate characteristics.

    • Neuronal speed and connectivity variations in specific brain regions.

    • Impact of environment, including stressors versus learning supports.

    • Recognition that both genetics and experience contribute to intellectual development, with genetics exerting more influence at the extremes of the intelligence spectrum, while most individuals experience greater environmental impacts.