IQ: Its Role, Relevance, and the Controversies Surrounding It

This article is based on a comprehensive video titled “What Does IQ Actually Measure?” by Veritasium. The video explores the concept of Intelligence Quotient (IQ), its history, applications, and the controversies surrounding it. It delves into the significance of IQ in various aspects of life, including education, military service, income, and longevity. It also addresses the dark history of IQ testing and its misuse in promoting racial differences in intelligence.


The Origins and Evolution of IQ

The concept of IQ originated from the work of Alfred Binet, a French psychologist who developed the Binet-Simon test in the early 20th century. The test was designed to identify children who needed extra help in school. However, when the test was brought to the U.S., it was modified and used to rank adults by intelligence. The American psychologist Lewis Terman further refined the test, creating the Stanford-Binet Intelligence Scale, which introduced the term “Intelligence Quotient” or IQ.

IQ and its Role in Education and Military Service

IQ tests have been used extensively in education and military service. In education, IQ tests can identify students who may need additional support or those who are gifted. In the military, IQ tests have been used to screen recruits. During the Vietnam War, the U.S. military lowered the IQ requirement to increase the pool of applicants. However, this resulted in recruits who were more likely to fail training and required more remedial training. This experience led the military to reinstate their IQ requirements.

IQ, Longevity, and Income

Studies have shown a correlation between IQ, longevity, and income. A Scottish study found that for every 15 point increase on the IQ test, individuals were 27% more likely to still be alive at age 76. Similarly, a study showed a clear tendency for income to increase with IQ, although the correlation was significant but small. However, the relationship between net worth and IQ was found to be even weaker.

The Dark History of IQ Testing

IQ testing has a dark history, particularly in the U.S., where it was used to support the eugenics movement. The belief that intelligence was inherited and unchangeable led to laws enabling forced sterilization of people who failed to meet a certain threshold on an IQ test. This history has led many people to disregard IQ today.

The Misuse of IQ and the Flynn Effect

IQ has been misused to promote the idea of racial differences in intelligence. However, this is a gross misrepresentation of the data. The Flynn Effect, named after researcher James Flynn, observed that the average results of IQ tests have increased steadily over the past century, suggesting that cultural changes can affect average scores on IQ tests.

The Limitations and Misconceptions of IQ

IQ tests do not necessarily measure what they are believed to measure. They are influenced by factors such as motivation, training, test-taking strategy, and anxiety. Moreover, IQ tests are not culture-fair as they claim to be. Different cultures perceive and interpret the test differently, which can influence the results.

The Role of IQ in Modern Society

Despite its limitations and controversies, IQ testing still plays a role in modern society. It is used in forensic neuroscience, particularly in death penalty cases, to determine intellectual disability. IQ testing can also help identify individuals with strong intellectual abilities who haven’t otherwise been able to demonstrate them. However, it is crucial to remember that IQ does not determine someone’s worth. It is just one aspect of a person’s capabilities and potential.

IQ and Job Performance

Research has consistently shown a positive correlation between IQ and job performance. In a meta-analysis of 85 years of research in personnel selection, Schmidt and Hunter (1998) found that general mental ability, which is closely related to IQ, was the best overall predictor of job performance and attainment of training. This correlation was observed across all types of jobs, suggesting that higher IQ individuals are generally more capable of understanding and adapting to complex job demands.

IQ and Health Outcomes

IQ has also been linked to health outcomes. In a longitudinal study, Batty et al. (2007) found that lower childhood IQ was associated with higher rates of hospital admissions for injuries in adulthood. This suggests that cognitive abilities may play a role in understanding and adhering to safety measures. Furthermore, a study by Calvin et al. (2011) found that higher childhood IQ was associated with a lower risk of adult mortality, indicating that cognitive abilities may influence health behaviors and decision-making.

IQ and Socioeconomic Status

The relationship between IQ and socioeconomic status (SES) has been a subject of extensive research. In a study by Strenze (2007), a meta-analysis of the literature, it was found that IQ was a significant predictor of SES, including income, occupation, and education. This suggests that cognitive abilities can influence social mobility and economic success. However, it’s important to note that this relationship is complex and can be influenced by various factors such as family background, education, and opportunities.

The video


In conclusion, while IQ is not the sole determinant of an individual’s success or worth, it plays a significant role in various aspects of life, like job performance, health outcomes, and socioeconomic status. Remember that IQ is just one aspect of human intelligence and potential, and it should not be used to stereotype or limit individuals.


  1. Veritasium. (2023, August 4). What Does IQ Actually Measure? [Video]. YouTube.
  2. Batty, G. D., Deary, I. J., & Gottfredson, L. S. (2007). Premorbid (early life) IQ and later mortality risk: systematic review. Annals of epidemiology, 17(4), 278-288.
  3. Calvin, C. M., Deary, I. J., Fenton, C., Roberts, B. A., Der, G., Leckenby, N., & Batty, G. D. (2011). Intelligence in youth and all-cause-mortality: systematic review with meta-analysis. International journal of epidemiology, 40(3), 626-644.
  4. Schmidt, F. L., & Hunter, J. (1998). The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. Psychological bulletin, 124(2), 262.
  5. Strenze, T. (2007). Intelligence and socioeconomic success: A meta-analytic review of longitudinal research. Intelligence, 35(5), 401-426.

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