IQ Test - World

    IQ Scale: Understanding Intelligence Score Ranges

    The IQ scale is a standardized scoring system where 100 represents the population average, with a standard deviation of 15 points. This means approximately 68% of all people score between 85 and 115.

    IQ Score Classifications

    145+ — Highly Gifted / Genius
    0.1% of population
    130–144 — Gifted
    2.1% of population
    115–129 — Above Average
    13.6% of population
    100–114 — Average (High)
    34.1% of population
    85–99 — Average (Low)
    34.1% of population
    70–84 — Below Average
    13.6% of population
    Below 70 — Extremely Low
    2.1% of population

    The Bell Curve Distribution

    IQ scores follow a normal (Gaussian) distribution—also called a bell curve. The majority of people cluster near the center (IQ 100), with progressively fewer people at the extremes. About 95% of the population scores between 70 and 130.

    Major IQ Test Scales

    The most widely used IQ tests include the Wechsler Adult Intelligence Scale (WAIS-IV), Stanford-Binet Intelligence Scales (5th Edition), and Raven's Progressive Matrices. All modern tests use a mean of 100 and standard deviation of 15, making scores comparable across instruments.

    The Flynn Effect

    Research by James Flynn documented that average IQ scores have risen approximately 3 points per decade worldwide since the early 20th century. This phenomenon means IQ tests must be periodically re-normed. Contributing factors include improved nutrition, education, healthcare, and cognitive stimulation from technology.

    Frequently Asked Questions

    IQ scores are categorized as follows: Below 70 is classified as extremely low, 70–84 as below average, 85–99 as average (lower range), 100–114 as average (upper range), 115–129 as above average, 130–144 as gifted, and 145+ as highly gifted or genius level. The average IQ score is 100 with a standard deviation of 15 points.

    Approximately 2.1% of the population scores above 130 on a standardized IQ test. This threshold is commonly used by organizations like Mensa as their minimum qualifying score. Only about 0.1% of people score above 145, which is often considered the genius threshold.

    Yes, IQ scores can fluctuate throughout a person's lifetime. Fluid intelligence—the ability to solve novel problems—typically peaks in the mid-20s and gradually declines, while crystallized intelligence—accumulated knowledge—tends to increase with age and experience. Education, health, and environmental factors also influence IQ scores.

    Both the Wechsler (WAIS) and Stanford-Binet scales use a mean of 100, but historically differed in standard deviation: Wechsler uses SD=15, while older Stanford-Binet editions used SD=16. The current Stanford-Binet 5 also uses SD=15. Wechsler provides separate Verbal and Performance IQ scores, whereas Stanford-Binet focuses on five cognitive factors.

    Yes, IQ tests are specifically designed so that 100 represents the population mean. The tests are periodically re-normed to maintain this average. Due to the Flynn Effect—a documented rise in average IQ scores over generations—a score of 100 today represents higher absolute cognitive ability than a score of 100 from 50 years ago.

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