Intelligence Testing | Abnormal Psychology (2023)

Learning Objectives

  • Explain the purposes and types of intelligence testing (including the Wechsler and Stanford-Binet intelligence tests and the Kaufman Assessment Battery for Children)

Intelligence Testing | Abnormal Psychology (1)

Figure 1. Starting from early primary school years, researchers and clinicians assess intelligence through standardized test batteries (i.e., IQ tests), as these tests are intended to be suitable for a wide age range.

Intelligence is among the oldest and longest studied topics in all of psychology. The development of assessments to measure this concept is at the core of the development of psychological science itself.

When might an IQ test be used? What do we learn from the results, and how might people use this information? While there are certainly many benefits to intelligence testing, it is important to also note the limitations and controversies surrounding these tests. For example, IQ tests have sometimes been used as arguments in support of insidious purposes, such as the eugenics movement (Severson, 2011). The infamous Supreme Court Case, Buck vs. Bell, legalized the forced sterilization of some people deemed “feeble-minded” through this type of testing, resulting in about 65,000 sterilizations (Buck vs. Bell, 274 U.S. 200; Ko, 2016). Today, only professionals trained in psychology can administer IQ tests, and the purchase of most tests requires an advanced degree in psychology. Other professionals in the field, such as social workers and psychiatrists, cannot administer IQ tests.

Inpsychology, human intelligence is commonly assessed byIQscores that are determined by IQ tests. However, there are critics of IQ tests who, while they do not dispute the stability of IQ test scores or the fact that they predict certain forms of achievement rather effectively, do on the other hand argue that to base a concept of intelligence on IQ test scores alone is to ignore many important aspects of mental ability.

For instance, individual differences in general intelligence are one of the strongest predictors of occupational attainment, social mobility, and job performance. People with higher general intelligence in childhood or early adulthood also tend to have better overall physical health, and have a longer life expectancy. Further, children with higher childhood IQ have a lower risk of developing dementia and of being diagnosed with schizophrenia spectrum disorder, major depression, or any anxiety disorder in adulthood. Understanding how differential IQ levels become associated with these life outcomes is crucial not only from a scientific point of view, but also for developing public policy and determining effective interventions.

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Why Measure Intelligence?

The value of IQ testing is most evident in educational or clinical settings. Children who seem to be experiencing learning difficulties or severe behavioral problems can be tested to ascertain whether the child’s difficulties can be partly attributed to an IQ score that is significantly different from the mean for their age group. Without IQ testing—or another measure of intelligence—children and adults needing extra support might not be identified effectively. While IQ tests have sometimes been used as arguments in support of insidious purposes, such as the eugenics movement (Severson, 2011), the following case study demonstrates the usefulness and benefits of IQ testing.

Why Test IQ?

Candace, a 14-year-old girl experiencing problems at school in Connecticut, was referred for a court-ordered psychological evaluation. She was in regular education classes in ninth grade and was failing every subject. Candace had never been a stellar student but had always been passed to the next grade. Frequently, she would curse at any of her teachers who called on her in class. She also got into fights with other students and occasionally shoplifted. When she arrived for the evaluation, Candace immediately said that she hated everything about school, including the teachers, the rest of the staff, the building, and the homework. Her parents stated that they felt their daughter was picked on because she was of a different race than the teachers and most of the other students. When asked why she cursed at her teachers, Candace replied, “They only call on me when I don’t know the answer. I don’t want to say, ‘I don’t know’ all the time and look like an idiot in front of my friends. The teachers embarrass me.” She was given a battery of tests, including an IQ test. Her score on the IQ test was 68.

What does Candace’s score say about her ability to excel or even succeed in regular education classes without assistance? Why were her difficulties never noticed or addressed?

Types of IQ Tests and Tasks

There are a wide variety of IQ tests that use slightly different tasks and measures to calculate an overall IQ score. The most commonly used test series is the Wechsler Adult Intelligence Scale (WAIS) and its counterpart, the Wechsler Intelligence Scale for Children (WISC). Other commonly used tests include the original and updated version ofStanford-Binet, and the Kaufman Assessment Battery for Children. We will discuss all of these.

Stanford-Binet Intelligence Test

The person best known for formally pioneering the measurement of intellectual ability is Alfred Binet. Binet was particularly interested in the development of intelligence, a fascination that led him to observe children carefully in the classroom setting. Along with his colleague Theodore Simon, Binet created a test of children’s intellectual capacity. Simon and Binet created individual test items that should be answerable by children of given ages. For instance, a child who is three should be able to point to her mouth and eyes, a child who is nine should be able to name the months of the year in order, and a twelve-year-old ought to be able to name sixty words in three minutes. Their assessment became the first IQ test.

(Video) The dark history of IQ tests - Stefan C. Dombrowski

IQor intelligence quotientis a name given to the score of the Binet-Simon test. The score is derived by dividing a child’s mental age (the score from the test) by their chronological age to create an overall quotient. These days, the phrase IQdoes not apply specifically to the Binet-Simon test and is used to generally denote intelligence or a score on any intelligence test. In the early 1900s, the Binet-Simon test was adapted by a Stanford professor named Lewis Terman to create what is, perhaps, the most famous intelligence test in the world, the Stanford-Binet (Terman, 1916). The major advantage of this new test was that it wasstandardized. Based on a large sample of children, Terman was able to plot the scores in a normal distribution, shaped like a bell curve (see Fig. 1). To understand a normal distribution, think about the height of people. Most people are average in height, with relatively fewer being tall or short, and fewer still being extremely tall or extremely short. Terman (1916) laid out intelligence scores in exactly the same way, allowing for easy and reliable categorizations and comparisons between individuals.

Weschler Intelligence Scales

A look at another modern intelligence test—the Wechsler Adult Intelligence Scale (WAIS)—can provide clues to a definition of intelligence itself. Motivated by several criticisms of the Stanford-Binet test, psychologist David Wechsler sought to create a superior measure of intelligence. He was critical of the way that the Stanford-Binet relied so heavily on verbal ability and was also suspicious of using a single score to capture all intelligence. To address these issues, Wechsler created a test that tapped a wide range of intellectual abilities. The the Wechsler Adult Intelligence Scale (WAIS) assesses people’s ability to remember, compute, understand language, reason well, and process information quickly (Wechsler, 1955).David Wechsler’s approach to testing intellectual ability was based on the fundamental idea that there are, in essence, many aspects to intelligence. The Stanford-Binet test reflected mostly verbal abilities, while the Wechsler test also reflected nonverbal abilities. The Stanford-Binet has also been revised several times and is now similar to the Wechsler in several aspects, but the Wechsler continues to be the most popular test in the United States.

The current version of the test, the WAIS-IV, which was released in 2008, comprises 10 core subtests and five supplemental subtests, with the 10 core subtests yielding scaled scores that sum to derive the Full Scale IQ. With the WAIS-IV, the verbal/performance IQ scores from previous versions were removed and replaced by the index scores. The General Ability Index (GAI) was included, which consists of the similarities, vocabulary, and information subtests from the verbal comprehension indexand the block design, matrix reasoning and visual puzzles subtests from the perceptual reasoning index. The General Ability Index (GAI) is clinically useful because it can be used as a measure of cognitive abilities that are less vulnerable to impairments of processing speed andworking memory.

Intelligence Testing | Abnormal Psychology (3)

Figure 2. The WAIS uses a variety of components to determine a person’s IQ score, including verbal, memory, perceptual, and processing skills.

(Video) AP Psychology - Unit 5 - Intelligence & Testing

Index Scores and Scales

There are four index scores representing major components of intelligence:

  • Verbal Comprehension Index (VCI)
  • Perceptual Reasoning Index (PRI)
  • Working Memory Index (WMI)
  • Processing Speed Index (PSI)

Two broad scores, which can be used to summarize general intellectual ability, can also be derived:

  • Full Scale IQ (FSIQ), based on the total combined performance of the VCI, PRI, WMI, and PSI
  • General Ability Index (GAI), based only on the six subtests that the VCI and PRI comprise.
Tasks grouped by index
IndexTaskCore?DescriptionProposed abilities measured
Verbal ComprehensionSimilaritiesIntelligence Testing | Abnormal Psychology (4)Describe how two words or concepts are similar.Abstract verbal reasoning; semantic knowledge
VocabularyIntelligence Testing | Abnormal Psychology (5)Name objects in pictures or define words presented to them.Semantic knowledge; verbal comprehension and expression
InformationIntelligence Testing | Abnormal Psychology (6)General knowledge questionsDegree ofgeneral informationacquired from culture
ComprehensionQuestions about social situations or common conceptsAbility to express abstract social conventions, rules, and expressions
Perceptual ReasoningBlock DesignIntelligence Testing | Abnormal Psychology (7)Put together red-and-white blocks in a pattern according to a displayed model; this is timed, and some of the more difficult puzzles award bonuses for speedVisual spatial processing and problem solving; visual motor construction
Matrix ReasoningIntelligence Testing | Abnormal Psychology (8)View an array of pictures with one missing square, and select the picture that fits the array from five optionsNonverbal abstract problem solving,inductive reasoning
Visual PuzzlesIntelligence Testing | Abnormal Psychology (9)View a puzzle in a stimulus book and choose from among pieces of which three could construct the puzzleVisual spatial reasoning
Picture CompletionSelect the missing part of a pictureAbility to quickly perceive visual details
Figure WeightsView a stimulus book that pictures shapes on a scale (or scales) with one empty side and select the choice that keeps the scale balancedQuantitative reasoning
Working MemoryDigit SpanIntelligence Testing | Abnormal Psychology (10)Listen to sequences of numbers orally and to repeat them as heard, in reverse order, and in ascending orderWorking memory, attention, encoding, auditory processing
ArithmeticIntelligence Testing | Abnormal Psychology (11)Orally administered arithmetic word problems; timedQuantitative reasoning, concentration, mental manipulation
Letter-Number SequencingRecall a series of numbers in increasing order and letters in alphabetical orderWorking memory, attention, mental control
Processing SpeedSymbol SearchIntelligence Testing | Abnormal Psychology (12)View rows of symbols and target symbols, and mark whether or not the target symbols appear in each rowProcessing speed
CodingIntelligence Testing | Abnormal Psychology (13)Transcribe a digit-symbol code using a key. The task is time-limitedProcessing speed, associative memory, graphomotor speed
CancellationScan arrangements of shapes and mark specific target shapes within a limited amount of timeProcessing speed

TheWechsler Intelligence Scale for Children(WISC)

Intelligence Testing | Abnormal Psychology (14)

Figure 2. The (WISC), developed byDavid Wechsler, is an individually administeredintelligence testfor children between the ages of six and 16. The Fifth Edition (WISC-V; Wechsler, 2014) is the most recent version.

TheWechsler Intelligence Scale for Children(WISC) is an individually administeredintelligence testfor children between the ages of 6 and 16. The Fifth Edition is the most recent version.

The WISC-V generates a Full Scale IQ that represents a child’s general intellectual ability. It also provides five primary index scores: Verbal Comprehension Index, Visual Spatial Index, Fluid Reasoning Index, Working Memory Index, and Processing Speed Index. Five ancillary composite scores can be derived from various combinations of primary or primary and secondary subtests.

Five complementary subtests yield three complementary composite scores to measure related cognitive abilities relevant to assessment and identification of specificlearning disabilities, particularlydyslexiaanddyscalculia. Variation in testing procedures and goals can reduce time of assessment to 15–20 minutes for the assessment of a single primary index, or increase testing time to three or more hours for a complete assessment, including all primary, ancillary, and complementary indices.

Kaufman Assessment Battery for Children

TheKaufman Assessment Battery for Children(KABC) is a clinical instrument (psychologicaldiagnostic test) for assessing cognitive development. Its construction incorporates several recent developments in both psychological theory and statistical methodology. The test was developed byAlan S. KaufmanandNadeen L. Kaufmanin 1983 and revised in 2004. The Kaufman Assessment Battery for Children (KABC) also gives special attention to certain emerging testing needs, such as use withhandicappedgroups, application to problems oflearning disabilities, and appropriateness forculturalandlinguisticminorities. The authors rightly caution, however, that success in meeting these special needs must be judged through practical use over time. The KABC-II helps to identify an individual’s strengths and weaknesses in cognitive ability and mental processing. The information provided by the KABC-II can facilitate clinical and educational planning, treatment planning, and placement decisions.

(Video) Measuring Intelligence | Psychology

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This video explains some of the intelligence tests as well as some of the complications in measuring intelligence.

You can view the transcript for “Measuring Intelligence | Psychology” here (opens in new window).

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IQ:intelligence quotient, or name given to the score of the Binet-Simon test; the score is derived by dividing a child’s mental age (the score from the test) by their chronological age to create an overall quotient

Kaufman Assessment Battery for Children(KABC): a clinical instrument (psychologicaldiagnostic test) for assessing cognitive development

Stanford–Binet Intelligence Scales:an individually administeredintelligence testthat was revised from the original Binet–Simon Scale byLewis Terman, a psychologist at Stanford University

Wechsler Adult Intelligence Scale(WAIS): anIQ testdesigned to measureintelligenceandcognitive abilityin adults and older adolescents

(Video) Psychology: Intelligence Tests

Wechsler Intelligence Scale for Children(WISC): an individually administeredintelligence testfor children between the ages of six and 16


How do you pass an intelligence test? ›

Tips for taking an IQ test
  1. Read the instructions carefully. Read thoroughly to know exactly what the purpose of the test is. ...
  2. Calculate your time. Calculate your time. ...
  3. Skip hard questions. ...
  4. Don't guess recklessly. ...
  5. Go over your answers at the end.

What is a good intelligence test score? ›

The number actually represents how your results compare to those of other people your age. A score of 116 or more is considered above average. A score of 130 or higher signals a high IQ. Membership in Mensa, the High IQ society, includes people who score in the top 2 percent, which is usually 132 or higher.

What are the three problems with intelligence tests? ›

IQ tests have the potential to inaccurately measure an individual's intelligence and cause problems including low confidence, unrealistic expectations, and just a generally flawed understanding of a person's potential.

Is there a downside to intelligence testing? ›

There are also limitations to IQ tests that professionals need to be aware of. The tests provide a 'snapshot' of a child's responses at the time of taking the test. For various reasons, children may not demonstrate their full potential on the test.

What is the easiest way to solve IQ questions? ›

Top 15 IQ Questions Solved - YouTube

Is a IQ of 120 good? ›

Is a 120 IQ good? An IQ score of 120 is a good score since it means superior or above-average intelligence. A score of 100 is said to be the average IQ and anything above that is above average intelligence for the person's age.

Is 146 a high IQ? ›

85 to 114: Average intelligence. 115 to 129: Above average or bright. 130 to 144: Moderately gifted. 145 to 159: Highly gifted.

Do IQ tests mean anything? ›

IQ tests measure a variety of skills like working memory, fluid reasoning, verbal comprehension and more. But he notes the science suggests IQ tests are still not well equipped to provide meaningful scores for these separate abilities, and should be interpreted only as measuring someone's overall general intelligence.

What is the lowest recorded IQ? ›

There's no record of the lowest IQ ever. However, the lowest IQ score possible is zero.

Why do some psychologists oppose intelligence testing? ›

Many critics have argued that IQ tests ignore or underestimate the contribution of factors like emotion, social skills, motivation or even morality.

Is intelligence testing a useful method? ›

Standardized intelligence testing has been called one of psychology's greatest successes. It is certainly one of the field's most persistent and widely used inventions.

Are intelligence tests reliable? ›

The truth about intelligence: A guide for the confused

No wonder IQ tests are often considered controversial and flaky. But that simply isn't the case. “Despite the critiques, the intelligence test is one of the most reliable and solid behavioural tests ever invented,” says Rex Jung at the University of New Mexico.

Why are intelligence tests flawed? ›

IQ tests have been used for decades to assess intelligence but they are fundamentally flawed because they do not take into account the complex nature of the human intellect and its different components, the study found.

What are some of the pros and cons of intelligence testing? ›

The Pros & Cons of IQ Testing in Schools
  • Identifies Gifted Students. One benefit to IQ testing in elementary school is that tests like the Stanford Binet and Weschler IV can identify gifted students as early as pre-school or kindergarten. ...
  • Identifies Students at Risk. ...
  • Stifles Potential. ...
  • Lack of Diversity. ...
  • Validity of Testing.

What are some of the limitations of intellectual assessments? ›

List of the Cons of Intelligence Testing
  • It is challenging to design an independent test. ...
  • It can lead to the use of labels. ...
  • It does not measure all forms of intelligence. ...
  • It can lead to the development of stereotypes. ...
  • It will often test limited subject material. ...
  • It is information which is used inconsistently.
Apr 17, 2019

Who has highest IQ ever? ›

Marilyn Vos Savant (IQ - 228)

Louis, Missouri in 1946 when Marilyn Vos Savant was 10 years old, in an adult level Stanford-Binet Test found out that her IQ is 228. Due to this record-breaking result, her name was recorded in the Guinness Book of World Records.

What is the average IQ score? ›

Psychologists revise the test every few years in order to maintain 100 as the average. Most people (about 68 percent) have an IQ between 85 and 115. Only a small fraction of people have a very low IQ (below 70) or a very high IQ (above 130). The average IQ in the United States is 98.

Does IQ change with age? ›

Not generally. IQ tests are age adjusted, basically to take account of youth and inexperience (under 18) or age and diminishing speed.

Is IQ genetic? ›

Researchers have previously shown that a person's IQ is highly influenced by genetic factors, and have even identified certain genes that play a role. They've also shown that performance in school has genetic factors.

Can IQ be increased? ›

Although science is on the fence about whether you can raise your IQ or not, research does seem to suggest that it's possible to raise your intelligence through certain brain-training activities. Training your memory, executive control, and visuospatial reasoning can help to boost your intelligence levels.

How rare is a 125 IQ? ›

By the current "deviation IQ" definition of IQ test standard scores, about two-thirds of all test-takers obtain scores from 85 to 115, and about 5 percent of the population scores above 125.

Is 120 IQ gifted? ›

While different IQ tests have different score ranges, most IQ tests are set up to yield a mean score of 100 with a standard deviation of 15. For that reason, someone with an IQ score of 120 is generally considered intellectually gifted.

What is Albert Einstein's IQ? ›

What was Albert Einstein's IQ? Though some sources estimate theoretical physicist Albert Einstein's IQ was around 160, there is no indication he ever had his IQ tested, according to

Who has 300 IQ? ›

William James Sidis has the World's Highest IQ. Anywhere from 250 to 300 is his IQ score, almost twice the score of Albert Einstein. At the age of eleven, William famously entered Harvard University, becoming the youngest person to enter, also, claimed to be conversant in 25 languages.

Which country has most intelligent people? ›

Ranked: The 25 Smartest Countries In The World
RankingCountryAverage IQ
3Hong Kong105.7
4South Korea104.6
21 more rows
Jan 11, 2019

Can someone with a low IQ be successful? ›

Evidence is ramping up that IQ is "real, partially hereditary, and predictive of important life outcomes," such as health and prosperity, but that doesn't mean a high IQ ensures success—or that a low IQ guarantees failure, Scott Alexander writes for Vox.

What are two criticisms of intelligence tests? ›

Finally, IQ tests do not offer information on motivation, emotion, attitudes, and other similar factors that may have a strong bearing on a person's success in school and in life. Other critics hold that intelligence is far too complex to be precisely measured by tests.

How do you know if an intelligence test is biased? ›

Compare IQ scores of two groups. If no group different exists, test is not biased. (e.g., “Take a random sample. If scores are similar between ethnic or other groups, the test is not biased.”)

What is a major problem with intelligence tests mentioned in the text? ›

What is a major problem with intelligence tests mentioned in the text? Some ethnic and socioeconomic groups perform better than others on IQ tests. Which of the following is a description of the Remote Associates Test (RAT)?

Are intelligence tests culturally biased? ›

Intelligence tests contain cultural bias—they contain a strong bias that is in favor White, middle class groups; for example: (a) the tests measure knowledge and content that are more familiar to White, middle class Page 22 6 students than to diverse students; (b) the language on these tests is more familiar to White, ...

What are 2 advantages of intelligence testing? ›

What are the advantages of using intelligence tests in recruitment?
  • It makes recruitment more targeted. ...
  • It saves time and money. ...
  • You get future insights into your candidates. ...
  • Your candidates are treated equally in testing. ...
  • Recruitment is adapting to an ever-changing working environment.
Oct 3, 2020

What are the uses and misuses of intelligence test? ›

Intelligence tests serve many useful purposes if used by trained professionals. Uses of Intelligence Test: Intelligence test assists in selection, counselling, guidance, self analysis and diagnosis. Abuses of Intelligence Test: Intelligence test causes ill effects/misuses/abuses if used by naive testers.

What questions are on an IQ test? ›

What IQ test types are there? In a classic IQ test you will generally find questions related to numerical reasoning, logical reasoning, verbal intelligence and spatial intelligence. An IQ test that primarily measures abstract reasoning, either inductive or deductive, will often be a non-verbal IQ test.

How is intelligence tested in psychology? ›

The most widely used intelligence tests include the Stanford-Binet Intelligence Scale and the Wechsler scales. The Stanford-Binet is the American adaptation of the original French Binet-Simon intelligence test; it was first introduced in 1916 by Lewis Terman, a psychologist at Stanford University.

Is it possible to measure a person's intelligence accurately? ›

"There is no such thing as a single measure of IQ or a measure of general intelligence." More than 100,000 participants joined the study and completed 12 online cognitive tests that examined memory, reasoning, attention and planning abilities.

How do you solve IQ shapes based questions? ›

Can you Answer this IQ Test Question: Which Shape ... - YouTube


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