7.5

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 and Intelligence Testing

While you’re likely familiar with the term "IQ" and associate it with the idea of intelligence, what does IQ really mean? IQ stands for intelligence quotient, which describes a score earned on a test designed to measure intelligence. Psychologists describe intelligence (or more aptly, intelligences) in various ways, and IQ tests—the tools designed to measure intelligence—have been a subject of ongoing debate throughout their development and use.

Applications of IQ Testing

When might an IQ test be used? The results provide insight into cognitive abilities and can serve various purposes:

• Academic assessment: Identifying students who may need special educational interventions.
• Clinical evaluation: Understanding an individual's cognitive strengths and weaknesses.
• Legal applications: Assessing competency in court scenarios.

Despite the benefits, there are also limitations and controversies associated with IQ tests. For example, historically, IQ tests have sometimes been misused to support harmful ideologies, such as the eugenics movement, exemplified in the Supreme Court case Buck v. Bell, which resulted in about 65,000 sterilizations (Buck v. Bell, 274 U.S. 200; Ko, 2016). Given the serious implications, only professionals trained in psychology can administer IQ tests today, with the purchase of most tests requiring an advanced degree in psychology.

Measuring Intelligence

The human understanding of intelligence is often limited when solely focusing on traditional or academic types. Critical questions arise, such as:

• How can intelligence be measured accurately?
• How do we ensure that rage of tests measure intelligence validly?

Historical Development of IQ Tests

The IQ test has been synonymous with intelligence for over a century. In the late 1800s, Sir Francis Galton developed the first broad test of intelligence (Flanagan & Kaufman, 2004), although he was not a psychologist, his contributions laid groundwork still felt today (Gordon, 1995).

Reliable intelligence testing truly began in the early 1900s with Alfred Binet, who was tasked by the French government to create an intelligence test for children to identify those who might struggle academically. This test focused on several verbally based tasks. American researchers recognized the value of such testing, leading to further developments.

Binet's Contributions and Stanford-Binet Scale

In particular, Louis Terman, a professor at Stanford, modified and standardized Binet’s test, testing children across various ages to determine average scores—this effort led to the Stanford-Binet Intelligence Scale (Terman, 1916).

• Standardization: The test was administered consistently to a large sample, leading to a bell curve representation of scores.
• Norming: This involved collecting data from a large population to create referential scores, which helps interpret future test results.
• Norms demonstrate what a group knows, not what they should know.

Remarkably, the updated version of the Stanford-Binet test remains in use today.

Wechsler's Contributions

In 1939, David Wechsler, influenced by his work with World War I veterans, developed a new IQ test in the U.S. that integrated several subtests designed to assess a diverse array of verbal and nonverbal skills. He believed intelligence encompassed “the global capacity of a person to act purposefully, to think rationally, and to deal effectively with his environment” (Wechsler, 1958, p. 7).

• This test was initially named the Wechsler-Bellevue Intelligence Scale and later revised to the Wechsler Adult Intelligence Scale (WAIS), which remains one of the most extensively used intelligence tests (Boake, 2002).

Today, there are three notable IQ tests by Wechsler:

1. Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV)
2. Wechsler Intelligence Scale for Children (WISC-V)
3. Wechsler Preschool and Primary Scale of Intelligence - IV (WPPSI-IV) (Wechsler, 2012).

These tests are invaluable in educational and community settings and are routinely normed and standardized for ongoing accuracy. The latest iteration, the WISC-V, comprises 14 subtests yielding scores across five indices—Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed.

• The Full Scale IQ score is derived from score interpretation based on cognitive abilities related to test performance.

The Flynn Effect

Interestingly, the periodic recalibrations of IQ tests led to a phenomenon known as the Flynn effect, which observes that each generation scores higher than the preceding one on IQ tests. James Flynn, who described this trend, maintained that increased IQ scores do not equate to greater overall intelligence in younger generations (Flynn, Shaughnessy, & Fulgham, 2012).

Validity and Controversies of Intelligence Testing

Despite advancements in testing, the fundamental question remains on the validity of intelligence tests. Current tests evaluate competencies beyond verbal skills, but the specific abilities assessed, and the results' applicability, continue to be hotly debated (Gresham & Witt, 1997; Flynn, Shaughnessy, & Fulgham, 2012; Richardson, 2002; Schlinger, 2003).

Capital Punishment and People with Intellectual Disabilities

The case of Atkins v. Virginia is a landmark Supreme Court case relevant to discussions of IQ and disabilities.

• Event Details: On August 16, 1996, Daryl Atkins and William Jones robbed and killed Eric Nesbitt, with Atkins subsequently assessed to have an IQ of 59, indicating an intellectual disability.
• Though found guilty and sentenced to death, Atkins' defense argued that his mental capacity should mitigate his punishment.
• The Supreme Court ruled in June 2002 that executing individuals with intellectual disabilities is considered ‘cruel and unusual punishment’ under the Eighth Amendment.

The court emphasized the clinical definitions of mental retardation, noting:

“Clinical definitions of mental retardation require not only subaverage intellectual functioning, but also significant limitations in adaptive skills… Mentally retarded persons frequently know the difference between right and wrong and are competent to stand trial. Because of their impairments…they have diminished capacities… to engage in logical reasoning…”
(The court, Atkins v. Virginia, 2002).

Implications of the Ruling

This ruling highlighted societal beliefs regarding intelligence and its effect on criminal culpability. States were allowed to define intellectual disability, which led to variations in execution eligibility.

• In a subsequent ruling, Hall v. Florida, the Supreme Court established that IQ scores cannot solely determine a defendant's death penalty eligibility (Roberts, 2014).

The Bell Curve and Intelligence Tests

The outcomes of intelligence tests typically follow the bell curve, illustrating a normal distribution of IQ scores among the population.

• The average IQ score is established as 100.
• Standard deviations help contextualize the distribution of scores within this bell curve—a critical descriptor of test results.

In modern IQ testing, one standard deviation equals 15 points. For instance:

• A score of 85 is “one standard deviation below the mean.”
• A score of 115 is “one standard deviation above the mean”.
• 68% of the population scores between 85 and 115.
• An IQ score of 130 or higher is classified as superior.

Diagnosing Intellectual Disabilities

An individual scoring approximately 70 or below across cognitive and adaptive functioning could be diagnosed with an intellectual disability (ID). The DSM categorizes ID into four subtypes, each with distinct characteristics:

High IQ Individuals

On the other end of the IQ spectrum, scores placing individuals in the highest ranges (e.g., IQ of 130 or higher) show a capacity for giftedness in educational systems. Early misconceptions viewed the highly intelligent as maladjusted, but findings, particularly from Lewis Terman's longitudinal study of children with IQs over 135, debunked this myth. Terman's research demonstrated that these individuals ultimately became successful and well-adjusted adults.