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How accurate are IQ tests?

Based on the provided sources and the scientific consensus they describe, professionally developed IQ tests are considered among the most accurate, reliable, and valid assessment tools in the field of psychology [2, 4]. The accuracy of an IQ test can be understood in three main ways: its reliability, its validity, and its predictive power.

1. Reliability (Consistency)

Reliability refers to how consistently a test measures what it aims to measure. IQ tests demonstrate high reliability, meaning an individual will get a very similar score if they take the same test or a comparable one on different occasions [2].

• Test-Retest Reliability: IQ scores are remarkably stable throughout an individual’s life, especially after adolescence. The correlation between IQ scores measured years apart is very high, often exceeding .90 (where 1.0 is a perfect correlation) [2, 4].
• Internal Consistency: The various parts of a single IQ test are highly correlated with one another, indicating that they are all measuring the same underlying construct [2].

2. Validity (Measuring the Right Thing)

Validity concerns whether a test truly measures what it purports to measure—in this case, general intelligence (also known as the g factor) [1, 2]. The consensus in the field is that IQ tests are valid measures of general cognitive ability [4, 5].

• Construct Validity: IQ tests effectively capture the g factor, which is the common element that underlies performance on all cognitive tasks [1, 2].
• Freedom from Bias: A common misconception is that IQ tests are culturally biased. However, extensive research has found that modern, professionally developed tests are not biased against native-born minority groups. They predict outcomes like academic performance and job success equally well across different racial and ethnic groups, meaning a person with an IQ of 115, regardless of their background, tends to perform similarly to others with that score [2, 4].

3. Predictive Power (Real-World Outcomes)

Perhaps the most significant evidence for the accuracy of IQ tests is their ability to predict a wide range of important life outcomes. While IQ is not the only factor, it is often the single most powerful predictor [1, 2].

• Academic Success: IQ scores are strong predictors of school grades and overall academic achievement [1, 2].
• Job Performance: The correlation between IQ and job performance is about .50, making it one of the best predictors of success at work, especially in complex jobs [1, 2].
• Life Outcomes: Higher IQ scores are correlated with higher income, better health, and even a longer lifespan [1, 2].

The Gap Between Science and Public Perception

Several sources note a significant disconnect between the strong scientific consensus on the accuracy of IQ tests and the general public’s understanding. This gap is often attributed to poor media reporting, ideological critiques that are not supported by data, and outdated information being taught in introductory psychology courses [3, 5, 6]. Many common criticisms, such as those popularized by Stephen Jay Gould’s The Mismeasure of Man, have been widely refuted by experts in the field but persist in public discourse [3, 6].

In conclusion, the research literature overwhelmingly supports the view that IQ tests are accurate instruments. They are highly reliable over time, validly measure general intelligence, and are powerful predictors of academic, professional, and personal life outcomes [1, 2, 4].

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Sources

1. Riot IQ. “Breaking the Taboo.” https://www.riotiq.com/articles/breaking-the-taboo
   • This article argues that while discussing IQ is a social taboo, it is a scientifically robust and highly predictive measure of real-world outcomes like academic and professional success. It emphasizes that IQ is the single most powerful psychological trait for predicting these outcomes.
2. The Nature-Nurture-Nietzsche Newsletter. “12 Things Everyone Should Know About IQ.” https://www.stevestewartwilliams.com/p/12-things-everyone-should-know-about
   • This article presents a summary of the scientific consensus on intelligence. It states that IQ tests are among the most reliable and valid instruments in psychology, that scores are highly stable, and that they are powerful predictors of many life outcomes.
3. Quillette. “Why Is Most Journalism About IQ So Bad?” https://quillette.com/2024/10/30/why-is-most-journalism-about-intelligence-so-bad/
   • This essay argues that media coverage of intelligence research is often inaccurate and ideologically driven, creating public confusion. It asserts that the scientific consensus on the reliability and validity of IQ tests is strong, contrary to what is often reported.
4. Personality and Individual Differences. “Myths and Misconceptions About Intelligence: A Study of 35 Myths.” https://archive.jwest.org/Research/Furnham2021-MythsIntelligence.pdf
   • This academic paper systematically debunks common myths about intelligence. It provides evidence that IQ tests are reliable, valid, and generally not culturally biased, and that they are strong predictors of important life outcomes.
5. Archives of Scientific Psychology. “What Do Undergraduates Learn About Human Intelligence? An Analysis of Introductory Psychology Textbooks.” https://archive.jwest.org/Research/Warne2018-UndergradIntelligence.pdf
   • This research paper analyzes psychology textbooks and finds that they often provide incomplete or outdated information about intelligence. It highlights the gap between the expert consensus on the validity of IQ tests and what students are taught.
6. Intelligence. “Communicating Intelligence Research: Media Misrepresentation, the Gould Effect, and Unexpected Forces.” https://archive.jwest.org/Research/Correspondence2018-CommunicatingIntelligenceResearch.pdf
   • This academic correspondence discusses the challenges of communicating intelligence research to the public. It points to media misrepresentation and the lingering influence of debunked critiques (the “Gould Effect”) as reasons for public misunderstanding of the established accuracy of IQ tests.
7. Douance. “IQ: From Causes to Consequences.” https://douance.org/qicc/references.html
   • This source is not an article but a comprehensive bibliography of scientific papers on intelligence. Its inclusion demonstrates the vast body of research that underpins the conclusions about IQ test validity and predictive power discussed in the other sources.