Intelligence can be difficult to define and challenging to measure or truly understand. An intelligence test is intended to measure a person’s cognitive ability compared to his peers. Intelligence assessment has been labeled as one of the psychology profession’s greatest successes. It has also divided the scientific community since its inception in the early 1900s.

There are many methods and instruments for measuring intelligence at any age. Basically, intelligence is the ability to learn from experience, think independently, adapt to a change in a setting or situation and solve problems.

Instruments for Measuring Intelligence

There are a few widely used intelligence tests. The Wechsler Adult Intelligence Scale has been in use for more than 75 years. The Kaufman Brief Intelligence Test is relatively new and is used primarily to assess children.

The Cattell’s Culture-Fair Intelligence Exam focuses on measuring the general intelligence of the test taker over specific skill sets, as does Raven’s Progressive Matrices.

Why Assessing Intelligence Is Important

Assessing intelligence offers a way for the individual and instructors or physicians to better understand the capabilities of that person as well as to tailor education plans or therapy to assist the person in meeting her full potential. However, an intelligence test does not give a full picture of the complete value of any one individual.

Even critics of intelligence tests find intelligence exams to be valuable to a point. When you are better able to understand your capabilities, you are better able to reach goals and be successful. An intelligence test is just one part of a larger process of testing for individuals who put such tests in high regard.

What Is Intelligence?

How to best conceptualize and measure intelligence has long been debated and criticized. However, it is generally agreed that a person’s ability to solve problems, relate to others and write and speak well enough to be understood and to communicate with others is a good foundation for simple human intelligence.

Intelligence can be defined as the cognitive or intellectual abilities that are required to obtain knowledge and to apply and use that knowledge to solve problems.

How IQ Is Used

The level of intelligence can be used as a beneficial tool in many ways. Instruments for measuring intelligence are often used to help a student who is struggling or who has shown above-average capabilities.

The results of an IQ test can be used by employers to hire or promote employees, particularly in engineering, science or math-based industries.

An intelligence assessment can also assist an individual who is struggling with behavioral issues and the administrators or legal authorities who are helping him.

Key Terms for Intelligence Testing

Generally, all instruments for measuring intelligence use the same terms. These include:

  • G – This is the abbreviation for general intelligence. General intelligence is an idea developed in psychometric investigations of cognitive skills that summarizes positive connections among different cognitive tasks.

  • Intelligence Quotient

    The score that is derived from one of the many different standardized tests that are used to attempt to measure an individual’s intelligence.

    Psychometrician – The person who creates, administers and scores an intelligence assessment exam.

    IQ – Intelligence quotient.

Critics of Intelligence Exams

An intelligence test also has its detractors and supporters. The exact definition of intelligence and how it is measured and by what form has continued to be a point of contention with medical professionals as well as with parents and those in the legal field.

All exams and assessments, from standardized testing such as the SAT to the Stanford-Binet Intelligence Scale, have fallen under criticism for one reason or another. Most of the criticism refers to cultural discrepancies in environmental factors, including:

  • Quality of education
  • Access to school systems
  • Race
  • Gender

How Intelligence Assessments Started

The idea of measuring intelligence has been around for centuries. Alfred Binet and his colleague Henri Simon were the first to be credited with creating a standardized test to identify children in Paris in the early 1900s who were learning impaired. It was intended to assist teachers in better educating children.

The Binet-Simon method consisted of a wide variety of questions that asked children to complete sentences, define words, draw pictures, name objects and construct sentences, among other questions.

The Evolution of Intelligence Testing

That eventually morphed into a test to measure above-average intelligence. The term "IQ" got its start during the first decade of the 20th century when German psychologist William Stern defined IQ as a ratio of an estimated mental age of a person rather than their actual chronological age.

Stern’s formula was rather basic: If a 10-year-old child has the mental capability of a 12-year-old, that child’s IQ is 120 (100 x 12/10).

What Different IQ Levels Mean

If you have taken an IQ test and received a score, then you may be confused about what it truly means. The scale for classifying IQ scores was originally created by the psychologist Lewis Terman and continues to be used today. It seems almost archaic in its labeling.

  • Under 70 – Definitive feeble-mindedness
  • 70 to 79 – Borderline deficiency
  • 80 to 89 – Dullness
  • 90 to 109 – Normal or average level of intelligence
  • 110 to 119 – Superior intelligence
  • 120 to 140 – Very superior intelligence
  • 140 and above – Genius or near genius

The gifted IQ level is between 125 and 134, with highly gifted students falling in the 135 to 144 level. The general public falls into the following categories on average:

  • 99.5 percent of IQ scores fall between 60 and 140
  • 70 percent of IQ scores fall between 85 and 115
  • 50 percent of IQ scores fall between 90 and 110

Definition of Intelligence

It can be tricky to define intelligence. In general, intelligence tests are psychological exams that are specifically designed to measure a wide variety of mental functions. This can be subjective. The measurements include:

  • Reasoning
  • Comprehension
  • Judgment

An IQ exam can show individuals what level they are on the IQ scale. The final number is often compared to the age group of the person who took the test. The typical intelligence test has a mean score of 100 points with a standard deviation of 15 points. This means that 95 percent of test takers will score within the interval of 70 to 130, and 68 percent of the population will score an IQ within the interval of 85 to 115.

Wechsler Adult Intelligence Scale

The first intelligence test that was explicitly designed to test an adult population was published by David Wechsler in 1939.

One of the most widely used intelligence tests, the Wechsler Adult Intelligence Scale was created by a Romanian-American psychologist who studied memory loss in World War I battle-weary soldiers. He expanded to include children and found that the intelligence of an individual is directly predisposed to the biological and environmental influences around him, as does persistence.

It quickly became a popular exam for measuring intelligence in a broad range of ages and groups and was named the Wechsler Adult Intelligence Scale, or WAIS.

The Wechsler Scale

The WAIS provides four individual index scores for the major components of intelligence. These are:

  • Processing Speed Index
  • Verbal Comprehension Index
  • Perceptual Reasoning Index
  • Working Memory Index

There are subtests for each of these indexes that are compiled to derive two broader intelligence scores, which are the Full Scale IQ and the General Ability Index. The Full Scale IQ is made up of the scores from all four of the indexes. The General Ability Index uses only the six subtests that are related to the Verbal Comprehension Index and the Perceptual Reasoning Index.

The WAIS has 10 core and five supplemental subtests that are divided into separate sections. Each subtest receives a score that is then averaged into an overall Full Scale IQ score.

Other Types of Intelligence

While most psychologists agree that general intelligence exists and can be measured to a degree, they also agree that there is specific intelligence. This is a measure of a specific skill in a narrow domain or domains.

Fluid intelligence is the capacity to learn new ways of solving old problems and performing activities in different ways. Crystalized intelligence is the accumulated knowledge of the world to which individuals are introduced throughout their lives.

Kaufman Brief Intelligence Test

In 1990, Alan Kaufman and Nadeen Kaufman created the Kaufman Brief Intelligence Test, or KBIT. It is individually administered to measure verbal and nonverbal intelligence in children age 4 and above.

The KBIT is a highly specialized exam that measures cognitive abilities. It must be administered by a trained health care professional. It considers the child’s cognitive progression and intellectual strengths and weaknesses. The KBIT scores are based on three components:

  • Verbal – Assessed crystalized ability
  • Nonverbal – Fluid reasoning assessment
  • Overall IQ composite – Based on an intelligence assessment tool

The correctly answered questions are added up to a raw points score that is then converted into standard measurements that are based on an overall standardized scoring model with a median score of 100. The KBIT scores range from 40 to 160 with the gifted score landing in the 125 range. The average score falls between 90 and 110.

Purpose of Intelligence Testing

The main purpose of an intelligence assessment is to obtain a general idea of the individual’s potential intellect. The intent is to assist a person and assessors to better understand a person’s potential and to build on that capability.

The exams center around a set of stimuli that is designed to yield a score that is based on the specific test taker’s model of what is considered to be the factors of intelligence. Tests are typically given as separate sections rather than a long, arduous examination.

Howard Gardner’s Eight Specific Intelligence Subjects

Many critics of intelligence testing believe that it is too limited in scope. To account for a broader range of human potential in both children and adults, Dr. Howard Gardner created eight main intelligences in 1983. These are:

  • Interpersonal – Has the ability to understand and interact with others in an effective manner

  • Intrapersonal – Is capable of having insight about the self and motivations

  • Kinesthetic – Ability to move well in a coordinated fashion for sports, dancing or other physical activity

  • Linguistic – Shows an ability to speak and write well to communicate clearly

  • Logical-mathematical – Able to solve problems with logic and mathematical skills

  • Musical – Shows an ability to enjoy and/or perform music

  • Naturalistic – Can recognize, relate, understand and identify animals, plants and a variety of other living things

  • Spatial – The ability to reason and consider objects in a three-dimensional way. This is also called picture thinking.

These different intelligences can also be referred to as people smart (interpersonal), self smart (intrapersonal), word smart (linguistic intelligence), number/reasoning smart (logical-mathematical), body smart (kinesthetic), music smart (musical) and nature smart (naturalistic).

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About the Author

Kimberley McGee is an award-winning journalist with 20+ years of experience writing about education, jobs, business trends and more for The New York Times, Las Vegas Review-Journal, Today’s Parent and other publications. She graduated with a B.A. in Journalism from UNLV. Her full bio and clips can be seen at www.vegaswriter.com.