IQ Full Form: Intelligence Quotient

An Intelligence Quotient (IQ) is a score from special tests. These tests measure human intelligence. Earlier, IQ was calculated in a simple way. A person’s actual age was divided by their mental age. After that, this figure was multiplied by 100. The IQ score was the final number.

Today, IQ is measured differently. Raw scores are adjusted to fit a normal curve. The average score is set at 100. The standard deviation is 15. Most people score between 85 and 115. Very few people score below 70 or above 130.

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Full Form of IQ

IQ stands for Intelligence Quotient. It is a score given after testing a person’s intelligence. These tests include different small parts or subtests. The final IQ score shows the person’s overall intelligence level.

What is IQ?

IQ scores can change in different situations. There are numerous ways to assess someone’s IQ. An individual’s IQ score indicates how intelligent they are in comparison with others. IQ can be assessed using a variety of standardized tests. An IQ of 100 is considered standard.

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History of IQ

Even before IQ tests existed, people tried to judge intelligence. They did this by watching behavior in daily life. Even today, this type of observation is still useful. It helps confirm IQ test results. Both observation and testing depend on how we define “intelligence.” Errors can happen in both methods.

The English scientist Francis Galton tried to make the first intelligence test. He worked on measuring human differences. He believed intelligence came from heredity. He did not mean genes. He thought intelligence was linked to things like reflexes and head size. In 1882, he opened the first mental testing center.

In 1883, he wrote about his ideas. He could not prove any link between intelligence and physical traits. He stopped this research later. Alfred Binet and Théodore Simon had more success in 1905. They made the Binet–Simon test. This test measured verbal skills in children. It helped identify children who needed extra help in school. Their test showed a child’s mental age.

For example, a 6-year-old passing tests meant for 6-year-olds had a mental age of 6. Binet and Simon believed intelligence was complex. They said intelligence could not be fully measured by numbers alone. In 1910, Henry Goddard translated their test into English.

It was revised at Stanford University by Lewis Terman in 1916. It became the Stanford–Binet test. This test was very popular in the USA for many years. In 1912, William Stern coined the term “IQ”. It stands for Intelligenzquotient in German.

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General Intelligence (g factor)

IQ tests use many types of questions. Some are visual. Some are verbal. They may ask about math, vocabulary, or general facts. In 1904, Charles Spearman studied test scores. He found that students who did well in one subject often did well in others. He said this showed a general mental ability. He called this “g” for general factor. He also noted there were smaller abilities for specific tasks. These were called “s” factors. The IQ score usually measures this general ability, g.

IQ Tests in World War I

The US Army had to test recruits during World War I. Tests for this were created by Robert Yerkes and others. They created both verbal and nonverbal tests. These helped place men in the right military jobs. The tests became famous. After the war, psychology gained respect. More jobs and funding went to psychologists. Group IQ tests became common in schools & companies.

These tests had problems. They often reflected cultural knowledge more than true intelligence. They also supported racist and anti-immigration ideas. Some believed IQ was fully inherited and fixed. This led to policies like the Immigration Restriction Act of 1924. L.L. Thurstone later suggested there are seven types of intelligence. His ideas influenced future theories.

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The Rise of Wechsler IQ Tests

In 1939, David Wechsler made a new IQ test. It became popular in the 1960s. Wechsler’s test had many subtests. It measured both verbal and nonverbal skills. The Stanford–Binet test was also updated over time. Today, the Wechsler tests are the most widely used in the USA.

IQ Testing and Eugenics

Eugenics aimed to improve the human gene pool. It excluded people seen as weak or unfit. Eugenics was popular in the USA in the early 1900s. The American eugenics movement was inspired by Francis Galton. He believed talent and intelligence came from heredity. Henry Goddard was a supporter of eugenics. He pushed IQ tests in schools, courts, and immigration checks.

He used the term “feeble-minded.” He said these people should not have children. He supported sterilization to prevent births. Laws forced over 60,000 people in the USA to be sterilized. The Supreme Court supported this in 1927.

Nazi Germany even copied ideas from California’s sterilization program. Though eugenics faded after World War II, some ideas returned in new forms. Today, genetic testing raises fresh ethical questions about intelligence.

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Cattell-Horn-Carroll (CHC) IQ Theory

In 1941, Raymond Cattell proposed two types of intelligence. One is fluid intelligence (Gf). It helps solve new problems through reasoning. The other is crystallized intelligence (Gc). It comes from knowledge and experience. Fluid intelligence can decline with age. Crystallized intelligence stays steady. Later, John Horn added more types of abilities.

In 1993, John Carroll added a new theory. He made a model with three layers. At the top is general intelligence (g). In the middle are broad abilities. At the bottom are narrow, specific skills. In 1999, these ideas merged into the CHC Theory.

It shapes most modern IQ tests today. Not all tests measure every ability in this theory. Older tests only measured verbal & nonverbal skills. Newer tests give a full picture of strengths and weaknesses

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Modern IQ Tests

Many IQ tests are used in English-speaking countries. The most common test for adults is the Wechsler Adult Intelligence Scale (WAIS). The most common test for children is the Wechsler Intelligence Scale for Children (WISC). Other popular tests include:

Stanford–Binet Intelligence Scales

1. Woodcock–Johnson Tests of Cognitive Abilities
2. Kaufman Assessment Battery for Children
3. Cognitive Assessment System
4. Differential Ability Scales

The term “IQ” is not always used to describe test results. Other assessments of IQ include:

1. Raven’s Progressive Matrices (RPM)
2. Cattell Culture Fair III (CFIT)

1. Reynolds Intellectual Assessment Scales (RIAS)
2. Thurstone’s Primary Mental Abilities
3. Kaufman Brief Intelligence Test (KBIT)
4. Multidimensional Aptitude Battery II
5. Das–Naglieri Cognitive Assessment System (CAS)
6. Naglieri Nonverbal Ability Test (NNAT)
7. Wide Range Intelligence Test (WRIT)

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IQ Reliability

Psychologists say IQ tests are generally reliable. Reliability means the test gives similar results if taken again. A good test gives stable scores over time. However, small changes in scores are common.

This means any score has a range of uncertainty. Modern IQ tests usually have a confidence interval of about ten points. Some tests claim the error is as small as 3 points. But these small errors may not capture all mistakes.

Many factors affect scores. Low motivation or high anxiety can lower a score. For people with very low IQ, the confidence range may be as big as 40 points. Very high IQ scores are less reliable than average ones. Scores over 160 are often viewed as doubtful. Below is an example of IQ scores from different tests for the same pupils: