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In 1905, psychologists Alfred Binet and[br]Théodore Simon

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designed a test for children who were [br]struggling in school in France.

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Designed to determine which children[br]required individualized attention,

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their method formed the basis[br]of the IQ test.

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Beginning in the late 19th century,

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researchers hypothesized that cognitive[br]abilities like verbal reasoning,

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working memory, and visual-spatial skills

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reflected an underlying general [br]intelligence, or g factor.

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Simon and Binet designed a battery of [br]tests to measure each of these abilities

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and combine the results [br]into a single score.

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Questions were adjusted for each [br]age group,

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and a child’s score reflected how they [br]performed relative to others their age.

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Dividing someone’s score by their age [br]and multiplying the result by 100

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yielded the intelligence quotient, or IQ.

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Today, a score of 100 represents [br]the average of a sample population,

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with 68% of the population [br]scoring within 15 points of 100.

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Simon and Binet thought the skills [br]their test assessed

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would reflect general intelligence.

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But both then and now,

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there’s no single agreed upon [br]definition of general intelligence.

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And that left the door open for people[br]to use the test

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in service of their own preconceived [br]assumptions about intelligence.

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What started as a way to identify those[br]who needed academic help

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quickly became used to sort [br]people in other ways,

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often in service of deeply flawed [br]ideologies.

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One of the first large-scale [br]implementations

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occurred in the United States during WWI, [br]when the military used an IQ test

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to sort recruits and screen them [br]for officer training.

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At that time, many people [br]believed in eugenics,

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the idea that desirable and [br]undesirable genetic traits

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could and should be controlled in [br]humans through selective breeding.

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There were many problems with [br]this line of thinking,

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among them the idea that intelligence[br]was not only fixed and inherited,

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but also linked to a person’s race.

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Under the influence of eugenics,

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scientists used the results of the[br]military initiative

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to make erroneous claims that certain[br]racial groups

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were intellectually superior to others.

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Without taking into account that [br]many of the recruits tested

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were new immigrants to the United States

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who lacked formal education [br]or English language exposure,

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they created an erroneous [br]intelligence hierarchy of ethnic groups.

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The intersection of Eugenics and IQ[br]testing influenced not only science,

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but policy as well.

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In 1924, the state of Virginia [br]created policy

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allowing for the forced sterilization of [br]people with low IQ scores—

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a decision the United States [br]supreme court upheld.

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In Nazi Germany, the government [br]authorized the murder of children

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based on low IQ.

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Following the Holocaust and the [br]civil rights movement,

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the discriminatory uses of IQ tests

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were challenged on both [br]moral and scientific grounds.

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Scientists began to gather evidence [br]of environmental impacts on IQ.

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For example, as IQ tests were periodically[br]recalibrated over the 20th century,

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new generations scored consistently[br]higher on old tests

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than each previous generation.

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This phenomenon, known [br]as the Flynn Effect,

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happened much too fast to be caused [br]by inherited evolutionary traits.

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Instead, the cause was likely [br]environmental –

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improved education, better [br]healthcare, and better nutrition.

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In the mid-twentieth century,

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psychologists also attempted [br]to use IQ tests

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to evaluate things other than [br]general intelligence,

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particularly schizophrenia, depression,[br]and other psychiatric conditions.

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These diagnoses relied in part on the[br]clinical judgment of the evaluators,

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and used a subset of the tests used [br]to determine IQ––

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a practice later research found does [br]not yield clinically useful information.

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Today, IQ tests employ many similar[br]design elements and types of questions

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as the early tests,

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though we have better techniques for[br]identifying potential bias in the test.

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They’re no longer used to diagnose[br]psychiatric conditions.

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But a similarly problematic practice [br]using subtest scores

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is still sometimes used to diagnose[br]learning disabilities,

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against the advice of many experts.

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Psychologists around the world [br]still use IQ tests

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to identify intellectual disability,

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and the results can be used to [br]determine appropriate educational support,

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job training, and assisted living.

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IQ test results have been used [br]to justify horrific policies

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and scientifically baseless ideologies.

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That doesn’t mean the test itself [br]is worthless—

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in fact, it does a good job of measuring[br]the reasoning and problem-solving skills

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it sets out to.

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But that isn’t the same thing as[br]measuring a person’s potential.

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Though there are many complicated[br]political, historical, scientific,

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and cultural issues wrapped up [br]in IQ testing,

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more and more researchers [br]agree on this point,

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and reject the notion that individuals[br]can be categorized

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by a single numerical score.