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IQ Test: Score Range, History, Types and Usage

bell curve of iq test range scores
Samyak Lalit
Samyak Lalit | June 25, 2022 (Last update: July 11, 2022)

Samyak Lalit is an author and disability rights activist. He is a polio survivor and the founder of projects like Kavita Kosh, Gadya Kosh, TechWelkin, WeCapable, Dashamlav and Viklangta Dot Com. Website:

Intelligence Quotient, commonly referred to as IQ, is a very common term in general communication. However, very few people understand what it actually means. We have an large number of IQ tests available online that claim to measure one’s intelligence level. But, before you rely on such IQ tests to categorize yourself or others as intelligent or not-so-intelligent, you must understand these tests logically. In this write-up, we are discussing IQ tests, score ranges and their relevance. Keep reading!

What is an IQ Test?

Definition: IQ test is it as a standard assessment of various cognitive abilities of human beings. The assessment is aimed at measuring the intellectual abilities and potentials of an individual.

The cognitive abilities measured by IQ tests include working memory, verbal comprehension, fluid reasoning, etc.

History of IQ Test

Today IQ tests are seen as a way to measure the general intelligence level of a person. But, it was not always the case. IQ tests have a dark history. They have been used in the past to promote discrimination against some ethnic and racial groups. IQ tests were also led to the forced sterilization of thousands of people during the eugenics movement. So, let’s peep into the historical background of IQ tests so that we can appreciate their great transformation.

First proper attempt to develop an IQ test was made by Francis Galton, an English statistician. Galton was studying human diversity and the inheritance of Human traits. His study was based on his theory that the intelligence is largely a byproduct of heredity. He established the world’s first mental testing center in 1882 intending to prove his hypotheses. He developed an IQ test to gather data about human intelligence and its link with other visible inherited features like the size of the head, the grip of muscles, etc. Galton could not prove his point and had to abandon this research. However, his theory and studies formed a strong base for the eugenics movement in America. The movement resulted in institutional isolation and forced sterilization of thousands of people who were believed to be ‘feeble-minded’.

Later, it was the year 1905 when French psychologists developed the ‘Binet-Simon’ test to identify young children with ‘mental retardation’. The Binet-Simon test, developed by Alfred Binet, Victor Henry, and Theodore Simon is considered the basis for the modern IQ tests. Unfortunately, this first test was developed to pick out young children who do not mentally ‘fit’ with children of their age. The aim was not to give those children extra support out of the class but to remove them from school and care in an asylum. The psychiatrists claimed that children who fail the Binet-Simon test were not slow but ‘sick’ and they need to be sent to asylums. This IQ test and many of its ‘improved versions’ have been used for many purposes, including the selection of army officers in the United States during the first World War.

Types of Modern IQ Tests

Since the early experiments, IQ tests have transformed completely with the contributions from hundreds of scientists, psychologists, and psychometricians. Today, there are dozens of standard IQ tests that are used for measuring a person’s general intelligence level.

The most frequently used individual IQ test is Wechsler Adult Intelligence Scale (WAIS) for adults and Wechsler Intelligence Scale for Children (WISC) for school-going children. These tests were developed by David Wechsler a Romanian-American psychologist.

The other popular standard IQ tests that are used worldwide include the following:

  • Cognitive Assessment System
  • Wide Range Intelligence Test
  • Kaufman Assessment Battery for Children
  • Naglieri Nonverbal Ability Test
  • Das-Naglieri Cognitive Assessment System
  • Stanford-Binet Intelligence Scale
  • Universal Non-Verbal Intelligence Test
  • Multidimensional Aptitude Battery
  • Woodcock-Johnson Tests of Cognitive Abilities
  • Reynolds Intellectual Assessment Scales
  • Raven’s Progressive Matrices

The content of these IQ tests as well as their results vary considerably. A person may score high in one test and at the same time may score lower in the other test. The results of the same test taken over a period of time by the same person may also vary.

Uses of IQ Tests

IQ tests are used for various purposes. It should be noted that the results of IQ tests cannot be used solely to define a person’s characteristics, behavior, or potentials. The questions of an IQ test are used to judge different areas of intelligence and cognitive abilities like memory, numerical skills, spatial perception, and language abilities. They may also focus on the assessment of capacity to understand relationships, solve problems and remember important information.

Some of the usage of various IQ tests are as below:

  • Admissions in educational institutions
  • Hiring for different roles in jobs
  • Assessment and diagnosis of intellectual disabilities
  • Assessment of cognitive abilities in general

IQ Score Range

As discussed earlier, there are a large number of IQ tests. Though all these tests aim to assess ‘general intelligence’ the weightage of different cognitive abilities differs from test to test. This is the reason one definition cannot justify the scores given by different IQ tests.

Following are the IQ score ranges and their meaning based on the Wechsler series of IQ tests for adults and children.

IQ Range and its Meaning
IQ Test Score RangeDescriptive Classification
69 and below*Intellectually Disabled
70 to 79Borderline of Intellectual Disability
80 to 89Lower than Average IQ
90 to 109Average IQ
110 to 119Higher than Average IQ
120 to 129Intellectually Superior
130 and aboveVery Superior/Genius

When the test results of the IQ test for a population is plotted, it results in a bell-shaped graph. On this graph, the score of the majority of test-takers lies near or around the average score. Around 68% population of the world is supposed to be near the score of 100 (with a positive and negative deviation of 15). This means 68% of the test takers would score in the range of 85 and 115.

[*Note: There was a time when an IQ score below 70 was used to mark someone as intellectually disabled. Today, test scores alone cannot be used for the purpose. Many other factors and clinical tests are taken into consideration before the diagnosis of intellectual disability.]


IQ tests may be useful in many cases. However, one should never rely on IQ test results for judging oneself or others. A higher IQ test score is in no way a prediction of a person’s life success. Similarly, a person with a lower IQ may become very successful in their life. In fact, many experts are of the view that social and emotional skills are the better determinants of success as compared to intelligence.

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