By Dr. Edwin van Thiel, updated February 18, 2019

In science, the term intelligence typically refers to what we could call academic or cognitive intelligence. In their book on intelligence, professors Resing and Drenth (2007)* answer the question ‘What is intelligence?’ using the following definition: “The whole of cognitive or intellectual abilities required to obtain knowledge, and to use that knowledge in a good way to solve problems that have a well described goal and structure.”

In ordinary language, one could say that intelligence refers to how smart or clever you are.

The first intelligence tests used in the field of psychology

The scales designed by Binet and Simon were the first intelligent tests that became widely accepted at the beginning of the 20th century. The Alpha and Beta army tests, that were used in World war I to assess military personnel, became very popular.

In recent years, the Wechsler scales are the most widely used instruments in the field of psychology for measuring intelligence. The designer of these tests, Wechsler, published his first scale in the 1930s. He used material from the Binet Alpha and Beta tests to make his test. An important feature of his test was, that when calculating the IQ, this test took age into account. In other words, in the computation of the IQ, an age-correction takes place. Because of this feature, the IQ stays constant over the life span.

The Intelligence Quotient (IQ)

IQ is an acronym for Intelligence Quotient. So what is IQ? The IQ is a measurement of your intelligence and is expressed in a number.

A person’s IQ can be calculated by having the person take an intelligence test. The average IQ is 100. If you achieve a score higher than 100, you are smarter than the average person, and a lower score means you are (somewhat) less smart.

An IQ tells you what your score is on a particular intelligence test, often compared to your age-group. The test has a mean score of 100 points and a standard deviation of 15 points. What does this standard deviation mean? It means that 68 percent of the population score an IQ within the interval 85-115. And that 95 percent of the population scores within the interval 70-130.

Some examples

What does it mean when your IQ is 100? That means that half of the population scores higher than you. The other half scores lower than you. And what does it mean when you have an IQ of 130? That means that 97,5 percent of your age group scores lower than you. Only 2,5 percent scores higher.

Take a look at a nice graph explaining more scores at meaning of an IQ score.

Further reading: Increasing your IQ and multiple intelligences. You can also take a free IQ test, or read the article on the history of the IQ test.

* Resing, W., & Drenth, P. (2007). Intelligence: knowing and measuring. Amsterdam: Publisher Nieuwezijds