What is the average IQ? We break down the normal distribution, explaining why most people score between 85 and 115 and what deviating from this range implies.
Dr. Russell T. WarneChief Scientist
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The average IQ is 100. This is not a coincidence; it is built into how IQ scores are calculated. When scientists develop an IQ test, they administer it to a large, representative sample of people and then set the scoring system so that the mean equals 100. This makes interpretation straightforward: a score of 100 means someone performed exactly as well as the typical person in the development sample.
How Is the Average IQ Determined?
Test creators recruit their development sample (also called a “norm sample”) that mirrors the population the test is designed for, matching characteristics like age, sex, education level, geographic region, and race/ethnicity. The sample’s collective performance becomes the standard against which all future examinees are compared.
The scoring system places the average at 100 with a standard deviation (which measures how spread out scores are) of 15. This statistical framework means that about 68% of people score between 85 and 115, and roughly 95% score between 70 and 130. Scores become increasingly rare the further they fall from the average. Only about 2% of people score above 130, and another 2% score below 70.
This approach is called a deviation IQ because it expresses how far someone's performance deviates from the average. It replaced the older "quotient" method (dividing mental age by chronological age) which had significant limitations, particularly for adults.
What Does an Average IQ Score Mean?
An IQ of 100 indicates typical cognitive ability for a person's age group. It does not mean someone is unintelligent or lacks potential. The average range, sometimes defined as 90 to 110, includes the largest portion of the population and encompasses people who function perfectly well in school, work, and daily life. It is an IQ range that often includes the sort of people who make society work: parents, plumbers, secretaries, truck drivers, etc.
Intelligence researchers have studied how IQ levels relates to real-world outcomes. People with average IQs can succeed in a wide variety of occupations, though certain professions tend to draw from higher ranges.Research on occupational differences shows that jobs requiring advanced education and complex problem-solving typically have higher average IQs, while jobs with simpler cognitive demands have lower averages. But considerable overlap exists, and individual variation within any job is substantial. In particular, there is often nothing stopping a very bright person from obtaining a job that has a low minimum IQ--if that is what they want or if that is what is available.
What Is the IQ Score Range?
IQ scores follow a normal distribution (also called, informally, a “bell curve”). Most people cluster near the middle, with fewer at the extremes:
• 130 and above: Very high (approximately 2% of population)
• 120-129: High (approximately 7%)
• 110-119: High average (approximately 16%)
• 90-109: Average (approximately 50%)
• 80-89: Low average (approximately 16%)
• 70-79: Borderline (approximately 7%)
• Below 70: Very low (approximately 2%)
These labels have changed over time and vary somewhat across tests. The Wechsler scales recently updated their terminology, replacing "Superior" with "Very High" and "Borderline" with "Very Low."
Scores at the extremes carry particular significance. An IQ below 70-75 is one criterion for intellectual disability, indicating significant limitations in cognitive functioning and adaptive behavior. High scores (above 120 or 130) often qualify individuals for gifted education programs. But these cutoffs are somewhat arbitrary. Someone with an IQ of 69 is not fundamentally different from someone with an IQ of 71.
Does Average IQ Vary Across Groups?
Average IQ can differ across demographic groups, though these differences require careful interpretation.
Age differences appear when comparing raw scores rather than age-normed IQs. Performance on tasks requiring fluid reasoning peaks in early adulthood and gradually declines, while crystallized knowledge remains stable or even increases until late in life. Because IQ tests compare people to others in their age group, these developmental patterns are accounted for in the final score.
Sex differences on overall IQ are negligible, typically less than a point, with neither sex consistently scoring higher. However,differences emerge on specific subtests. Males tend to score slightly higher on spatial tasks, while females tend to score slightly higher on verbal and processing speed tasks. These largely cancel out when combined into an overall IQ. Males also show greater variability (more males at both the high and low extremes). For most purposes in everyday life, this difference in variability has no impact. However, in situations that draw on a lot of people from high- or low-IQ groups, there is often a noticeable surplus of males. For example, a charity that works to help people with intellectual disabilities live independently will likely have more male clients than female clients.
Educational differences are substantial and unsurprising. People with more education tend to have higher IQs, reflecting both the genuine cognitive benefits of schooling and the tendency for smarter individuals to pursue more education.
Has the Average IQ Changed Over Time?
Throughout the 20th century, average performance on IQ tests increased substantially, which is a phenomenon called the “Flynn effect” after philosopher James Flynn, who documented it extensively. The gains averaged about 3 points per decade, meaning that someone scoring 100 on a test normed in 1950 might score around 115 on the same test normed in 1980.
15 points is a lot, but the Flynn effect does not mean people have become dramatically smarter. Research indicates that the Flynn effect primarily reflects changes in the non-g components of IQ (the specific abilities shaped by education, test-taking familiarity, and cultural changes) rather than increases in core intelligence. Society has, in effect, trained people to perform better on the specific tasks that IQ tests happen to measure. This is why tests require periodic re-norming to keep the average at 100 as population performance shifts.
Some countries have seen the Flynn effect slow, stop, or even reverse in recent decades, likely reflecting changes in educational emphasis rather than declining intelligence. But these changes do not reflect real changes in a population’s average intelligence. Rather, it merely means that scores from different historic time periods are not comparable.
Where Can I Find Out My IQ?
Anyone interested in learning where they fall relative to the average can take a professionally developed IQ test. TheReasoning and Intelligence Online Test (RIOT) provides this opportunity. Created by Dr. Russell T. Warne, who has over 15 years of experience in intelligence research, the RIOT is the first online IQ test designed to meet professional standards established by the American Psychological Association, American Educational Research Association, and National Council on Measurement in Education. Unlike amateur online tests that often produce inflated scores, the RIOT underwent expert review and includes a proper U.S.-based norm sample, providing results that can actually be trusted.
Watch “What Does an IQ Test Measure?” with Dr. Russell T. Warne on the Riot IQ YouTube channel to understand how average IQ scores are defined and interpreted.
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