William Sidis holds the title of having the highest IQ in the world! His IQ score was around 250-300. Was Sidis really intelligent, or did he just perform well on tests? Even though not all psychologists approve of IQ tests, they are one way that researchers measure intelligence.

• What is intelligence testing?

• What are different types of intelligence tests?

• How is intelligence testing used in psychology?

• What are some examples of intelligence testing in psychology?

• What are the disadvantages and advantages of intelligence testing?

The Definition of Intelligence Testing

Humans have been interested in studying intelligence for decades. Researchers want to know exactly what it is and how to measure it. While there is no definitive answer to those questions, psychologists have developed different methods for understanding and evaluating intelligence.

The word intelligence simply means to understand. Intelligence is more than what knowledge you possess. It is about what kinds of knowledge you thoroughly understand and excel at applying. In psychology, intelligence involves three different abilities:

1. Problem-solving
2. Gaining knowledge through experience
3. Adjusting to new situations

Intelligence testing is the measurement of an individual’s intelligence. These tests can be provided on paper or electronically and use different techniques to measure intelligence based on a person's circumstances and ability. Intelligence testing can be used in gathering data and conducting research. You have probably taken an intelligence test without even realizing it!

What is the Aim of Intelligence Testing?

Intelligence testing is the practice of measuring a person's performance on various diagnostic measures, i.e. intelligence tests to predict future behaviour, for interventions and on some occasions for the diagnoses of some illnesses, such as developmental disorders.

Types of Intelligence Tests

Most people will encounter two primary intelligence tests: achievement tests and aptitude tests. Achievement tests are typically offered in schools, but aptitude tests are offered to both students and adults.

Achievement Tests

Achievement tests are used to assess what you already know about a particular topic, school subject, or combination of subjects. This type of test is common in schools because they help educators measure if students learn and understand the topics presented in class.

Fig. 1 Achievement tests in schools, pexels.com

Although achievement tests usually focus on a specific subject and contain material that someone has already learned or been taught, scores still differ significantly from one person to another. This is partly because people learn at different paces and demonstrate what they have learned in different ways. Some people perform well on written tests, and others perform well when asked verbal questions.

Achievement tests show us what areas need improvement, but they should never be used to compare scores between test-takers. If a general score comparison is required, the average score can be used to evaluate if a single score is below or above the mean score. This is how scores are analyzed and evaluated in research studies. How well did you do on the test compared to the rest of your classmates?

Aptitude Tests

Intelligence Testing in Psychology

In psychology, there are multiple tests available to assess intelligence. We will focus on two different tests that are considered foundational to intelligence testing: the Binet-Simon Intelligence Scale and the Weschler Intelligence Scale. These tests are the foundation of the current IQ test.

The Binet-Simon Intelligence Scale

The first IQ test is the Binet-Simon Intelligence Scale, and it was named after the psychologists Alfred Binet and Theodore Simon. This test was created in France in 1904 when the French government asked Binet to create a way to determine which school children would face the most challenges in their academics. So, with the help of his colleague Theodore Simon, Binet began his research by focusing on areas like memory, attention, and critical thinking skills.

Binet and Simon focused on these areas because they believed that all three play important roles in how everyone learns. They created a 30-question test designed to test memory, attention, and critical-thinking skills. They included many different kinds of questions or tasks on the test. They might ask questions about the difference between two words (like the difference between hyper and excited) or ask the student to visually follow a moving object to test eyesight ability.

When the children took these tests, Binet observed that some would answer more advanced questions than he expected. Binet theorized that people have a mental age that may differ from their actual age. An individual’s mental age is based on how a person performs intellectually. In other words, Binet reasoned that although someone was 10 years old, they may perform at the cognitive level of a typical 15-year-old.

Fig. 2 Mental age vs. actual age, pexels.com

The Stanford-Binet Intelligence Scale

The second major IQ test is called the Stanford-Binet Intelligence Scale. It was developed at Stanford University by psychologist Lewis Terman. In this IQ test, Termon took Binet’s test and translated it into English so that it could be used with Americans. Terman updated some of the terms and included more questions to fit American education standards. Also, Terman used Binet’s theory of mental ages as the basis for coining the term Intelligence Quotient (IQ).

The Weschler Adult Intelligence Scales

Inspired by Binet’s theory of mental age but underwhelmed by Terman’s intelligence test, David Weschler decided to create his own version of an intelligence test - the Weschler Adult Intelligence Scales (WAIS; 1955). This test differs from both Binet’s and Terman’s versions because it was created for adolescents and adults and only contains questions (not tasks).

Weschler disagreed with the use of tasks in intelligence testing since they may discriminate against those who lack that capability. He believed that by only using questions the test would be more accessible, accurate, fair, and easier to administer. The test currently in use to test IQ is the fourth edition of the Weschler Adult Intelligence Scales (WAIS-IV). This test is not typically required, but it is available for use to assess IQ.

Weschler also produced two intelligence scales for children. Those tests are known as:

• The Wechsler Intelligence Scale for Children (WISC)

• The Wechsler Preschool and Primary Scale of Intelligence (WPPSI).

Examples of Intelligence Testing in Psychology

As mentioned earlier, the most recent version of the IQ test is called the WAIS-IV. This test is used with adolescents and adults. It contains 10 subtests that focus on four functions:

1. Verbal reasoning

2. Rational/critical thinking

3. Memory

4. Speed (i.e., how fast the person can mentally process certain questions)

Examples of questions on the test include spatial, mathematical, analogous, classification, and visual questions.

Example of Analogies

Example of Patterns

Example of Classification

The Advantages and Disadvantages of Intelligence Testing

Along with using intelligence testing as a measuring tool for mental capacity, it can also be used to assess low and high extremes. There are different score categories for IQ tests, but the low extreme refers to scores below 70. If someone scores below 70 on an IQ test, this is a sign of a possible intellectual disability. Intellectual disabilities can vary, but they typically include learning and communication difficulties and struggling with certain tasks. IQ tests can help screen for intellectual disabilities and identify those who need treatment and support.

The other end of IQ scores (the high extreme) is above the normal range. Extremely high scores indicate someone who may be gifted. Parents are not always able to realize that their child is gifted and that the child lacks the academic enrichment that they need. By assessing their child's intellectual capabilities, parents can provide the level of education their child needs.

While there are advantages to using IQ tests, one disadvantage is that IQ tests are costly. Depending on where you are located and how much information you want to receive, professional and accurate IQ tests can cost anywhere from $300 to $600. High prices like these discourage people from taking the test due to affordability.

Another disadvantage is that IQ tests do not account for test anxiety. Part of an IQ score is determined by mental processing speed. Some test-takers need more time time to perform well due to anxiety or other factors, and the test doesn't accommodate those needs. Many researchers question the validity or accuracy of IQ tests. IQ tests are only used for certain purposes, like screening for intellectual disabilities, but this is still problematic if the tests are not accurate. IQ tests can also be interpreted in different ways; scores can vary based on who gave you the test and who scored it!