How is IQ Measured: How Psychologists Gauge Cognitive Abilities

IQ is measured by assessing various aspects of an individual's cognitive abilities, encompassing mathematical proficiency, language skills, and reasoning capabilities.

IQ is measured through a series of standardized tests, wherein participants engage with a set of questions designed to assess their pattern recognition, memory, and problem-solving skills. Over the decades, the evolution of IQ measurement has witnessed the emergence of diverse tests, each accompanied by distinct IQ metrics. Generally, IQ was gauged by determining an individual's mental age, dividing it by their chronological age, and subsequently multiplying the result by 100. This historical approach laid the foundation for the multifaceted methods employed in contemporary IQ assessments.

How is IQ Measured?

The foundation of modern IQ testing in the United States can be attributed to the efforts of psychologist Henry Herbert Goddard. Goddard played a key role in translating an intelligence test developed by French psychologist Alfred Binet into English.

How is IQ measured

Originally designed by Binet to assess fundamental intellectual functions in schoolchildren and aid in mental health diagnoses, IQ tests have undergone significant evolution since then as in the history of IQ test. Presently, there are over a dozen distinct tests utilized for gauging intelligence.

Primarily, an IQ test is employed to assess an individual's reasoning and problem-solving abilities. Some of the most widely utilized IQ tests include:

  • Wechsler Intelligence Scale for Children (WISC-V)
  • Wechsler Intelligence Scale for Adults (WAIS)
  • Stanford-Binet Intelligence Scale
  • Differential Ability Scales (DAS)
  • Peabody Individual Achievement Test

Conducted by licensed psychologists, these tests typically consist of multiple parts. For instance, the WIS (Wechsler Intelligence Scale) includes 15 subtests, each measuring various facets of IQ, such as mathematical ability, language proficiency, reasoning skills, memory, and information-processing speed. IQ tests consist of a series of questions that evaluate different aspects of intelligence such as logical reasoning, problem-solving, verbal comprehension, and spatial awareness.

The final IQ score is derived by combining the results of these subtests, and adjustments are made based on the individual's age to provide a comprehensive and standardized evaluation of cognitive abilities. An IQ score of 100 is considered average, and scores above or below 100 represent deviations from the average in standard deviation units (e.g., a score of 115 is one standard deviation above the mean).

What Aspects of Cognitive Ability Do IQ Measure?

IQ, or Intelligence Quotient, is a numerical assessment of an individual's cognitive abilities as assessed through intelligence testing. While the concept of intelligence itself is complex and multifaceted, IQ tests are designed to measure specific cognitive skills and abilities that are believed to contribute to overall intellectual functioning. It's important to note that different IQ tests may have variations in how they assess working memory, and the specific subtests or indices may differ.

Verbal Comprehension

This component evaluates a person's ability to understand and use language effectively. It is the ability to use vocabulary, verbal reasoning, and the comprehension of written information.

The Verbal Comprehension Index on the WAIS assesses an individual's verbal abilities, including their understanding of vocabulary, verbal reasoning, and the ability to express ideas verbally. Questions in this section may involve defining words, understanding similarities and differences between words, and reasoning through verbal information.

Working Memory

Working memory is the ability to temporarily hold and manipulate information in one's mind. It involves questions or tasks related to mental arithmetic, remembering a sequence of numbers or letters, and solving problems with limited information.

One of the widely used IQ tests that specifically measures Working Memory is the Wechsler Intelligence Scale for Children (WISC) or the Wechsler Adult Intelligence Scale (WAIS), both developed by David Wechsler. Within these tests, you'll find a specific index or subtest that focuses on assessing working memory abilities.

The Working Memory Index (WMI) in the Wechsler tests typically includes tasks that require individuals to temporarily hold and manipulate information. Examples of tasks within this index may involve solving math problems mentally, recalling and rearranging a sequence of digits or letters, or performing other operations that engage working memory processes.

Perceptual Reasoning

This component assesses nonverbal and spatial reasoning abilities. Tasks and questions may involve visual-spatial processing, pattern recognition, and the ability to manipulate visual information without relying heavily on language.

The Wechsler Intelligence Scale for Children (WISC) and the Wechsler Adult Intelligence Scale (WAIS) are IQ tests that include a specific index or subtest for Perceptual Reasoning. In these tests, Perceptual Reasoning assesses nonverbal and spatial reasoning abilities.

Within the Wechsler tests, you'll find a Perceptual Reasoning Index (PRI) that comprises various subtests targeting these nonverbal and spatial reasoning skills. Examples of tasks within this index may include completing visual patterns, assembling objects, solving block design problems, and understanding spatial relationships.

Processing Speed

Processing speed measures how quickly an individual can process simple or routine information. This component is more about the speed of cognitive processing than the depth of understanding.

The Wechsler Intelligence Scale for Children (WISC) and the Wechsler Adult Intelligence Scale (WAIS) include a specific subtest that assesses Processing Speed. This subtest is designed to measure how quickly an individual can process simple or routine information.

In both the WISC and WAIS, the Processing Speed Index (PSI) is composed of tasks that require rapid cognitive processing. These tasks might include activities such as symbol search, digit symbol coding, or other exercises that demand quick visual-motor coordination and attention to detail.

How to Calculate IQ Score

The calculation of an IQ (Intelligence Quotient) score involves a standardized process that compares an individual's performance on an intelligence test to the performance of a representative sample of the population. Here are some general steps for how IQ scores are typically calculated:

Step 1: Conduct the IQ test

The individual takes an IQ test, which is designed to measure various cognitive abilities, such as verbal comprehension, working memory, perceptual reasoning, and processing speed.

Step 2: Score each subtest

The test is divided into subtests, each assessing a specific aspect of cognitive function. The raw scores (the number of correct responses) on each subtest are determined.

Step 3: Convert to standard scores

The raw scores are converted into standard scores. Standard scores are a way of expressing an individual's performance relative to the average performance of a reference group (often the general population).

The standard score has a mean (average) of 100 and a standard deviation of 15 in many IQ tests, resulting in a normal distribution or bell curve.

Step 4: Convert the final IQ Score

The final step involves converting the sub-scores into a single overall score, commonly referred to as the final IQ. This score is the one most commonly reported and discussed. The final IQ scale is adjusted for the individual's age to ensure that age-related differences in performance are taken into account.

It's important to note that while IQ tests are designed to provide a comprehensive overview of cognitive abilities, they do not capture the full spectrum of human intelligence. And how IQ is measured depends on the different types of IQ tests. Each test is designed with specific purposes, target populations, and assessment goals.