Are IQ Tests Valid?

Are IQ tests valid? Yes—professional IQ tests reliably measure intelligence and predict school & job success. Discover how valid IQ tests really are.

Dr. Russell T. WarneChief Scientist

The short answer is: it depends on what you're using the test for. Validity is not a property of tests themselves. Rather, validity is a property of how test scores are used or interpreted. An IQ score might be valid for hiring employees in cognitively demanding jobs, but entirely unjustified for determining who receives a medical transplant.

What Does Validity Mean?

In psychological testing, validity refers to the degree to which evidence supports a specific interpretation or use of test scores. Professional test creators follow guidelines established by the American Educational Research Association, the American Psychological Association, and the National Council on Measurement in Education in their Standards for Educational and Psychological Testing.

Test creators gather several types of validity evidence:

Content validity examines whether the test's tasks appropriately sample the domain being measured. Professional test creators have panels of experts review their content to ensure comprehensive coverage of intelligence.

Construct validity asks whether the test measures the psychological construct it claims to measure. For intelligence tests, this involves demonstrating that scores correlate with other cognitive measures in theoretically predicted ways.

Criterion validity examines whether scores predict important real-world outcomes like academic performance and job success.

Do IQ Tests Measure Intelligence?

IQ scores correlate with biological variables, including brain size, neural efficiency, and reaction time. If these tests measured something other than cognitive ability, such biological correlations would be impossible to explain.

IQ tests effectively measure the g factor or general intelligence. Charles Spearman discovered in 1904 that performance across diverse cognitive tasks correlates positively, explained by an underlying general ability. This finding has been replicated countless times across populations, ages, and test types.

The content also aligns with expert definitions. According to a 1997 consensus statement signed by over 50 leading researchers, intelligence is "a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience." IQ tests measure exactly these abilities.

In short, the evidence is very strong that IQ tests can be validly interpreted as measuring intelligence. Moreover, they can be used to make valid decisions about people’s lives in situations where intelligence is important, such as educational programs or hiring for some jobs. No test is perfect, but often IQ tests are among the best tools available for making decisions like these.

For a deeper look into the accuracy behind IQ tests, watch:

Where IQ Tests Fall Short

IQ tests measure general cognitive ability and specific cognitive skills, but not everything that contributes to success. Personality traits, motivation, creativity, emotional regulation, and social skills matter tremendously in life, yet don't appear on traditional intelligence tests.

IQ scores alone should rarely drive important decisions. Colleges evaluate grades, extracurricular activities, and other factors alongside test scores. High school grades capture punctuality, conscientiousness, and long-term goal completion, which are qualities that IQ tests miss but that predict success.

Tests can also fail when used outside their intended populations. A test developed for English-speaking American adults may not function properly in other cultures or countries. This doesn't indicate inherent bias, but it means the test is being misapplied. Professional standards require evidence that tests function properly before using them with new groups, though not everyone follows these guidelines.

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Dr. Russell T. WarneChief Scientist

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