Free Guide to Intelligence Testing Basics

What Intelligence Testing Is and How It Works

Intelligence testing measures how a person thinks, solves problems, and processes information. These tests look at different thinking skills rather than measuring if someone is "smart" or "dumb." The results provide information about strengths and challenges in areas like reasoning, memory, language understanding, and processing speed.

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Intelligence tests have been used since the early 1900s. The first modern test was created in France in 1905 to identify students who needed different learning approaches. Since then, psychologists and educators have developed many different types of intelligence tests. Each test focuses on slightly different skills and is used for different reasons.

The most commonly used intelligence tests today include the Wechsler Adult Intelligence Scale (WAIS), the Stanford-Binet Intelligence Scale, and the Woodcock-Johnson Tests of Cognitive Abilities. Schools often use other tests like the Cognitive Assessment System or the Kaufman Assessment Battery for Children. Each test has its own format and scoring system, but they all measure similar thinking skills in different ways.

An intelligence test typically takes between one and four hours, depending on which test is given. A trained professional, called a psychometrician or clinical psychologist, administers the test in a quiet room. The test taker responds to questions, solves puzzles, arranges objects, defines words, and completes other tasks. The test measures both speed and accuracy of responses.

Practical Takeaway: Intelligence tests measure thinking and problem-solving skills across multiple areas. Understanding what these tests do—and what they don't do—helps you understand what results mean. Tests show patterns of strengths and challenges, not an overall judgment of a person's worth or potential.

Understanding IQ Scores and What They Mean

An IQ score is a number that represents where someone's thinking abilities fall compared to others their age. The average IQ score is set at 100, with a standard deviation of 15 points. This means most people score between 85 and 115. Scores follow a pattern called a "bell curve," where most scores cluster in the middle and fewer scores appear at the very high or very low ends.

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Different score ranges indicate different performance levels. A score of 90 to 109 falls within the average range. Scores of 110 to 119 are considered "high average" or in the upper range of normal. Scores of 80 to 89 fall in the "low average" range. Scores above 130 are often considered very superior, while scores below 70 may indicate significant cognitive challenges. However, these categories vary slightly depending on which test was used and who interprets the results.

It's important to understand that IQ scores have limitations. A single number cannot capture all aspects of human thinking or potential. Someone with an average IQ score might excel at creative thinking, practical problem-solving, or understanding people's emotions—areas that traditional intelligence tests may not measure well. Additionally, cultural background, education level, language skills, and test anxiety can all influence scores. A person who is stressed, tired, or unfamiliar with test-taking may score lower than their actual abilities.

Subtest scores within an intelligence test often matter more than the overall IQ number. These subscores show which specific thinking areas are strong and which areas need more support. For example, someone might score very high on visual-spatial tasks but lower on processing speed. This pattern of strengths and challenges is more useful for understanding how a person thinks and learns than the overall score alone. Professionals use subtest patterns to identify specific learning needs and recommend tailored support strategies.

Practical Takeaway: IQ scores are reference points that compare thinking abilities to age peers. An overall IQ score tells only part of the story. The pattern of subtest scores reveals much more about how someone thinks, learns, and solves problems. Context matters—test results should always be interpreted along with real-world performance and individual circumstances.

Who Gets Intelligence Testing and Why

Schools request intelligence testing for several reasons. Teachers or parents may notice a student is struggling academically despite apparent effort, or conversely, a student may be bored because the regular curriculum is too easy. School districts use intelligence test results to determine if a student qualifies for special education services or gifted education programs. According to the U.S. Department of Education, approximately 14% of public school students receive special education services, and intelligence testing is often part of the evaluation process for identifying a student's needs.

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Psychologists and physicians also order intelligence testing for adults and children outside school settings. A person might seek testing to understand why they have difficulty concentrating, organizing, or completing tasks. Intelligence testing can provide information about whether attention issues or learning disabilities are present. Adults sometimes pursue testing later in life after recognizing patterns of struggle. For example, an adult might seek testing to understand why work tasks that seem routine to colleagues feel overwhelming.

Medical professionals may recommend intelligence testing when someone has experienced a brain injury, stroke, or illness that might affect thinking abilities. The test results provide a baseline against which future performance can be measured. This information helps doctors and therapists monitor recovery and adjust treatment plans. Additionally, intelligence testing can be part of evaluating someone for neurological conditions like dementia or for other medical concerns affecting cognition.

Legal and workplace situations sometimes involve intelligence testing. Courts may order psychological evaluations in custody cases or competency assessments. Employers rarely use intelligence tests for hiring decisions anymore due to legal concerns, but some specialized roles like pilot training or military positions may include cognitive assessments. In all these situations, the testing provides objective information about thinking abilities in addition to other factors being considered.

Practical Takeaway: Intelligence testing serves many different purposes depending on the situation. Whether in school settings, medical contexts, or legal matters, testing provides factual information about thinking abilities. Understanding the reason for testing helps you interpret results in the right context and recognize what information the test can and cannot provide.

Different Types of Intelligence Tests

The Wechsler tests are among the most widely used intelligence assessments. The WAIS is designed for adults ages 16 and older, while the Wechsler Intelligence Scale for Children (WISC) is used for children ages 6 to 16. Wechsler tests include subtests organized into four main areas: verbal comprehension, perceptual reasoning, working memory, and processing speed. The WAIS-IV, released in 2008, takes approximately 60 to 90 minutes to complete. Schools and psychologists favor Wechsler tests because they're well-researched, have strong reliability, and provide detailed information about different thinking areas.

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The Stanford-Binet Intelligence Scale, now in its fifth edition, measures five factors: fluid reasoning, knowledge, quantitative reasoning, visual-spatial processing, and working memory. This test is used for children as young as age two through adulthood. The Stanford-Binet is known for its strong measurement of reasoning abilities and adapts question difficulty based on answers, which means each person gets questions calibrated to their level. This adaptive approach makes testing more efficient and can feel more comfortable since people encounter questions at the right level of challenge—not too easy or too hard.

The Woodcock-Johnson Tests of Cognitive Abilities measure broad cognitive areas and narrow cognitive abilities. This test is valuable because it connects cognitive abilities directly to academic achievement, making it particularly useful in educational settings. The Kaufman Assessment Battery for Children (KABC-II) focuses on the processes people use to solve problems rather than specific knowledge. It's designed for children ages 3 to 18 and is often used when teachers suspect a learning disability.

Beyond these major tests, specialized assessments exist for specific purposes. The Universal Nonverbal Intelligence Test (UNIT) measures reasoning without requiring language skills, making it useful for people with hearing loss or those who speak different languages. The Cognitive Assessment System (CAS) measures planning, attention, simultaneous processing, and successive processing—areas connected to learning and school performance. Some organizations use brief screening tests like the Wechsler Abbreviated Scale of Intelligence (WASI) when only a quick estimate of general ability is needed. Each test has particular strengths depending on the person being tested and the reason for testing.

Practical Takeaway: Multiple intelligence tests exist, each with different strengths and purposes. The test used should match the reason for testing and the person's age and circumstances. Different tests may yield somewhat different scores for the same person, which is normal. Understanding which test was used helps explain what information the results provide.

What Intelligence Tests Do and Don't Measure