Module 3, Thinking and Intelligence: 7.5 Measures of Intelligence

Learning Objectives

  • By the end of this section, you will be able to:

    • Explain how intelligence tests are developed.

    • Describe the history of the use of IQ tests.

    • Describe the purposes and benefits of intelligence testing.

Understanding IQ

  • IQ stands for intelligence quotient.

  • IQ measures a score earned on a test designed to assess intelligence.

  • Intelligence may be defined in various ways, as psychologists specify different types of intelligences.

Usage and Controversy of IQ Tests

  • The application of IQ tests has been debated throughout history.

  • Benefits of IQ Testing: Provides information on cognitive abilities, essential for educational and psychological assessments.

  • Limitations and Controversies:

    • IQ tests have been misused for harmful purposes, such as in the eugenics movement.

    • Historical reference: Buck v. Bell (Supreme Court Case) sanctioned forced sterilization for individuals deemed 'feeble-minded' based on IQ tests, leading to approximately 65,000 sterilizations (Buck v. Bell, 274 U.S. 200; Ko, 2016).

    • Today, only trained professionals in psychology can administer IQ tests, with advanced degrees required to purchase most testing materials.

Development of Intelligence Testing

  • Intelligence tests measure cognitive abilities but must ensure valid measurement of intelligence.

  • Historical Context:

    • Late 1800s: Sir Francis Galton first broad test of intelligence (not initially a psychologist). His ideas influenced future IQ testing (Gordon, 1995).

    • Early 1900s: Alfred Binet developed a standardized intelligence test for the French government to identify school children needing additional help.

    • Utilized verbally based tasks.

    • Sampled various age groups leading to consistent score averages.

    • Louis Terman: Modified Binet’s work to create the Stanford-Binet Intelligence Scale (Terman, 1916).

    • Norming and standardization methods were established allowing a bell curve distribution of scores.

Definition of Key Terms

  • Standardization: Consistent administration, scoring, and interpretation of scores across diverse test environments.

  • Norming: The process of administering a test to a large population to establish average scores for various demographic groups.

  • Bell Curve: A graphical representation of the normal distribution of scores, embodying characteristics of a trait (e.g. intelligence).

Wechsler's Contributions

  • David Wechsler: Developed the Wechsler-Bellevue Intelligence Scale in 1939, focusing on various verbal and nonverbal abilities, elaborating on intelligence as a global capacity:

    • Defined intelligence in terms of the capacity to act purposefully, think rationally, and effectively deal with the environment (Wechsler, 1958, p. 7).

  • The test was renamed Wechsler Adult Intelligence Scale (WAIS) and is still widely used today.

  • There are three versions of Wechsler tests:

    • WAIS-IV: Wechsler Adult Intelligence Scale - Fourth Edition

    • WISC-V: Wechsler Intelligence Scale for Children - Fifth Edition

    • WPPSI-IV: Wechsler Preschool and Primary Scale of Intelligence - Fourth Edition (Wechsler, 2012).

  • The WISC-V includes 14 subtests and five indices: Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed.

The Flynn Effect

  • The Flynn effect describes the increase in IQ scores over generations, suggesting that each generation has higher scores than its predecessor.

  • James Flynn argues that higher scores do not imply greater intelligence, merely changes in test performances (Flynn, Shaughnessy, & Fulgham, 2012).

Implications of Intelligence Testing

  • Important ethical considerations arise in terms of the consequences of IQ testing results in educational or legal contexts.

  • Landmark Case: Atkins v. Virginia ruled that executing individuals with intellectual disabilities constitutes cruel and unusual punishment.

  • The Supreme Court's decision emphasized that those with disabilities often lack sufficient cognitive function for a fair trial.

Defining Intellectual Disabilities

  • Intellectual Disability (ID): Previously termed mental retardation; involves an IQ score below 70 with significant difficulties in adaptive functioning:

    • Subtypes defined in the DSM-5:

    • Mild: 85% of individuals; can function independently with basic skill competencies.

    • Moderate: 10% possess basic self-care skills but require oversight.

    • Severe: 5% require assistance in daily activities.

    • Profound: <1% may communicate minimally and need intensive support.

The Bell Curve in Intelligence Testing

  • On average, an IQ score is 100, with a standard deviation of 15 points.

  • Score Interpretation:

    • 68% of the population scores between 85 and 115 (average range).

    • Scores of 130 or above indicate superior intelligence.

Conclusion on the Value of IQ Testing

  • IQ testing serves critical functions in educational and clinical diagnoses, helping identify those needing support and facilitating access to resources.

  • Ongoing research is attempting to refine intelligence assessments for diverse contexts, aiming for more fair, reliable, and applicable outcomes.

  • Language evolution surrounding the term “intellectual disability” reflects societal attitudes toward cognitive impairments.

    • Shift from the term “mental retardation” has been influenced by stigmatization and now emphasizes dignity and respect.