What Is IQ?
Complete guide · 8 min read
IQ, or Intelligence Quotient, is a numerical measure of cognitive ability derived from standardized tests. It was designed to assess human intelligence relative to the general population.
Origins of IQ Testing
The concept of IQ was developed in the early 20th century. French psychologist Alfred Binet created the first intelligence test in 1905 to identify students needing academic support. German psychologist William Stern later introduced the "quotient" formula, dividing mental age by chronological age and multiplying by 100.
What Does IQ Actually Measure?
Modern IQ tests measure several cognitive domains: verbal comprehension (understanding and using language), perceptual reasoning (solving visual and spatial problems), working memory (holding and manipulating information), and processing speed (how quickly you can perform mental tasks).
No single test captures all facets of human intelligence. Creativity, emotional intelligence, and practical wisdom are not measured by standard IQ tests.
The IQ Scale
IQ scores follow a normal distribution with a mean of 100 and standard deviation of 15. About 68% of people score between 85 and 115. Scores above 130 are considered gifted, while scores below 70 may indicate intellectual disability.
Is IQ Fixed?
Research suggests IQ is partly genetic but also influenced by environment, education, nutrition, and mental exercise. Studies show IQ can change meaningfully throughout life, especially in childhood and adolescence.