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The intelligence quotient (IQ) is a standardized measure of cognition, or your ability to think, understand, reason, learn, and remember. By design, the average IQ score is 100.
Higher IQ scores are related to greater academic and professional achievement. Despite this correlation, IQ may be an imperfect measure of intelligence. Some critics suggest IQ scores reflect the ability to sit still, follow instructions, and test-take rather than innate intelligence or potential.
IQ scores are based on the results of tests measuring your spatial reasoning, verbal skills, logic, and reasoning skills. In general, the median, or the middle point in the distribution of all scores globally, is 100. You have an “average” IQ with a score between 90 and 109.
Older research from 2010 suggests the average IQ is 98 in the United States.
IQ averages vary by state. Researchers in 2022 found New Hampshire to have the highest (103.2) and New Mexico (95) to have the lowest. These results were based on several IQ tests, including the Program for the Assessment of Adult Competency (PIAAC) and National Assessment of Educational Progress (NEAP), given to 4th and 8th graders.
| IQ Score Range | Classification | Traits |
|---|---|---|
| Below 70 | Extremely Low | Severe limitations in intellectual ability |
| 70-79 | Very Low | Significant limitations in intellectual function |
| 80-89 | Below Average | Slight limits in cognitive ability |
| 90-109 | Average | Average intellectual function |
| 110-119 | High Average | Above-average cognitive abilities |
| 120-129 | Very High | High levels of cognitive and intellectual abilities |
| Above 130 | Extremely High | The highest levels of intellectual ability |
Just as average IQ can vary from state to state, there are also differences across the world. In a wide-ranging study published in 2010, researchers calculated IQ for 108 countries. They found the average to range from 64 (Mozambique) to 108 (Singapore).
| Country | Average IQ |
|---|---|
| Argentina | 93 |
| Botswana | 71 |
| China | 105 |
| Germany | 99 |
| India | 82 |
| Malaysia | 92 |
| Nigeria | 69 |
| Norway | 100 |
| South Korea | 106 |
| Turkey | 90 |
| United Kingdom | 100 |
| United States | 98 |
Many genetic and environmental factors may influence IQ. These include:
- Genetics: Researchers believe genetics determines about 50% of the differences between people. However, researchers haven’t identified any single gene associated with intelligence.
- Socioeconomic status: Children of families with higher incomes tend to score higher on IQ tests. This likely reflects the fact that wealthier kids get access to better schooling, making it easier for them to reach their potential.
- Parent education: Across several studies, researchers have found links between levels of parental education and their children’s IQ scores. On average, children of more educated parents score higher on these tests.
- Geographic location: On average, children living in cities or towns have a higher IQ than those in rural areas. As with economic status, this may be due to these areas having easier access to resources.
- Malnutrition: Another factor influencing adult IQ may be insufficient nutrition during infancy. In an older study from 2014 that tracked people over 40 years, researchers found that moderate to severe malnutrition during infancy led to increased chances of lower IQ and worse academic achievement.
- Low birthweight: Researchers have found associations between birth weight and IQ. In population studies, low and very low birthweight, including premature birth, led to lower average IQ.
- Physical activity: Researchers found that, on average, children who had less than five hours a week of physical activity scored lower than those who got more.
The first IQ test was introduced in 1905 by French psychologist, Alfred Binet and psychiatrist, Theodore Simon. Over the years, their test has been refined and revised, and other tests have been developed to measure IQ. Some of these tests include:
- Stanford Binet Intelligence Scale: The first IQ test administered to children in the U.S., the Stanford Binet test measures general intelligence as well as factors like crystallized intelligence (accumulated knowledge, facts and skills), fluid analytic intelligence (ability to think and reason), and working memory.
- Cognitive Assessment System (CAS): CAS is designed to test basic reasoning and processing abilities for children. In addition to an overall score, it measures learning strengths and weaknesses.
- Wechsler Adult Intelligence Scale (WAIS): A standard test of IQ in adults, this test measures four sets of abilities: verbal comprehension, processing speed (how quickly you synthesize information), perceptual organization (how you organize information), and working memory.
- Wechsler Primary and Preschool Scale of Intelligence (WPPSI-III): This Wechsler test is designed for young children. Like WAIS, it determines IQ by measuring abilities like verbal comprehension, processing speed, and reasoning.
- Wechsler Intelligence Scale for Children (WISC-V): Designed for children ages 6-16, this test measures overall IQ as well as other domains, like verbal comprehension, visual spatial reasoning, and working memory (ability to retain and manipulate information for reasoning and tasks).
- Kaufman Assessment Battery for Children (K-ABC): This IQ test measures problem-solving in ways that aren’t related to academic achievement.
- Universal Nonverbal Intelligence Test: This test is designed to measure IQ without relying on verbal or language abilities. Designed for children ages 5-18, it measures aspects of working memory, symbolic memory (ability to use and apply symbols), and reasoning.
Though IQ tests have a long history, they have caused controversy over the years. Broadly, this has to do with how the tests were developed and what they can actually measure. As popularly understood, it also has a problematic history. IQ has been used to reinforce racism and structural inequalities.
The perspectives of those that popularized these tests have been called into question. Dr. Henry Herbert Goddard—the psychologist who popularized these in the U.S. in 1908—argued that people with low IQ should be kept from having children. His work provided support for eugenics, a discredited movement based on racism and pseudoscience that had the goal of using selective breeding to “improve” human genetics.
Another criticism of IQ tests is that they are culturally biased. The researchers who developed IQ tests relied on data from white, middle- to upper-class students. As such, the assessments may be framed in ways that negatively impact the results among other populations.
In addition, critics note that IQ tests are based on narrow definitions of intelligence and limited in scope. They believe the tests focus only on certain cognitive skills like gathering and processing information, while leaving out others, like interpersonal skills and the ability to relate to others.
Intelligence quotient (IQ) is a measure of cognitive skills and overall intelligence. By design, the average IQ is 100.
Research suggests that many factors may influence IQ, including genetics, economic status, level of physical activity, and parental education. Some critics argue that these correlations may be more closely related to a person’s ability to take a test well, rather than their innate intelligence. IQ remains controversial.
