The History of IQ Testing

Charlee Iddon, Stephanie Thomas
  • Author
    Charlee Iddon

    Charlee has taught across all age ranges in history, English, mathematics and science for over 10 years. They have a master’s degree in Education from Canterbury Christ Church University and she is currently a doctoral candidate with Greenwich University, in the school of Education. They also have a PGCE with full qualified teacher status.

  • Instructor
    Stephanie Thomas
Discover the history of IQ tests and contributions by Alfred Binet & Henry Goddard. Learn the features of IQ tests, the IQ formula, and about modern IQ tests. Updated: 08/14/2022

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IQ Test History

The level of a person's intelligence is often referred to as their IQ. This stands for Intelligence Quotient. Throughout history, psychologists and people in positions of power have been interested in the intelligence levels of different people. Various tests and tools have been devised to learn about a person's intelligence level. This information about intelligence has been used for many purposes, immoral and discriminatory.

There have many different attempts to measure intelligence. In the late 1800s, intelligence testing was a large part of the American eugenics movement, which was started by Sir Francis Galton. Eugenics is the goal of improving the genetics in a population by reducing what the people in power consider to be inferior genes. The word eugenics means 'good genes'. Galton did not use an IQ test as such; his tests were exercises that involved the brain receiving information and providing a response. His tests were exercises called Sensorimotor tasks.

Following on from Galton's research in the 1890s, the psychologist James McKeen Cattell developed a series of mental tests to measure a person's intelligence. Later in 1904, the most famous early example in IQ test history was created by Alfred Binet. Under direction from the French government, Alfred Binet carried out studies to find the average levels of performance in students.

These studies used particular tests to assess the students' intelligence and find their Intelligence Quotient (IQ). The tests determined students' mental age; the results of this were divided by their actual age, called their chronological age. This calculation gives the IQ of the student. This is why it is called a quotient. A person's chronological age relates to how people develop their mental skills as they grow up.

IQ Formula

As a person's mental age is divided by the person's chronological age, the results are always compared to others of the same age as the test taker. The IQ test is calculated with the average score being 100, meaning that a score of 100 is expected for the average person. Scores below 100 are below average intelligence and above 100 are above average.


{eq}IQ\hspace{1mm}formula=\frac{Mental\hspace{1mm}age}{Chronological\hspace{1mm}age}*100 {/eq}


IQ Formula Example

Suppose the person testing is a 5-year-old child (their chronological age) with a mental age of a 7-year-old (from the IQ test results); the child's IQ would be 140. This result would mean that the child is well above average IQ.

{eq}\frac{7}{5}*100=140 {/eq}


The formula is important, particularly in modern IQ tests, because it compares people of the same age. Just using a person's test scores or mental age does not give an accurate representation of their IQ level and intellectual ability.

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Alfred Binet

Alfred Binet, who made the IQ test, was a French psychologist. He wanted to examine the differences in student levels of understanding and develop a way to identify if they had learning difficulties and disabilities. In 1905, when the IQ test was invented, the French government sought to make it a law that all children attend school. To ensure all children received a proper education, they needed to find out if a child was below average intellect. They were particularly interested in students who continually struggled in reading and mathematics. To test this, they instructed Alfred Binet to develop the IQ test.

Alfred Binet and his colleague Theodore Simon worked to create the Binet-Simon intelligence test. This test contained 30 questions designed to look at how people dealt with areas of skill not related to academic understanding, so they did not include mathematical questions, for example. The questions focused on skills such as memory and problem solving, as well as how much people could pay attention.

During the testing, it became apparent that children had different levels of ability at the same age. This led to the concept of mental age, the age at which a person's abilities would be at a certain point in life. If a young child had the same capabilities as someone older, they would have a higher mental age than their actual age.

The Binet-Simon test was very influential and became the foundation for other researchers to develop more IQ tests and studies. While this test was highly regarded and used as a basis for IQ levels and assessments, it is not without limitations and criticisms. Binet recognized that the tests were limited in assessing a person's intelligence. Many factors can affect the results of the quiz, such as the economic background. He also believed that a person's intelligence changes throughout life, so their base level of intelligence varies. Most importantly, the concept of intelligence is complex and cannot be reduced to a single number equivalent.

Henry Goddard and Eugenics

Intelligence testing has been used as a way for societies and influential people to discriminate and mistreat others. Sir Francis Galton used IQ testing in his pursuit of eugenics; he thought that if they discovered people with 'inferior genes' and prevented them from having children, it would improve the population's genetic makeup. Intelligence was not the only gene he deemed inferior, but it was an important element of eugenics.

Following this work, in 1917, Henry Goddard an American psychologist wanted to limit the immigration of those he considered inferior. He used intelligence testing on people who entered the United States at Ellis Island. His tests were heavily in favor and biased towards his own culture and language, simply because they were not created by someone who spoke English but also created to be used on people like Goddard. This was not considered, and the tests' results were used to claim that race and intelligence were linked. Goddard claimed that 'as many as 40-50% of immigrants were feebleminded.' In his reporting.

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Frequently Asked Questions

Who took the first IQ test?

Alfred Binet is credited with creating and taking the first IQ test. However, assessments of a person's intellect were used before Binet labeled a person's intelligence as IQ.

How was IQ originally measured?

Alfred Binet created the first IQ test and measured people's IQ with a series of tests. The results of these tests can give the participant's mental age. This was divided by their actual age and then multiplied by 100. This would give a measurement of the person's IQ.

When were IQ tests first given?

IQ tests were first given in 1904 by Alfred Binet. He created the IQ levels and tests for the French government to test children's abilities in schools.

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