Intelligence measurable? Limitations and influence of IQ tests

Intelligence is a difficult concept to define. There are numerous attempts to define the term, but they do not adequately cover what it stands for. This is because intelligence is an invented, hypothetical concept that is difficult to make concrete. Intelligence tests divide people into categories. But tests differ and therefore they do not all measure the same thing. The question is to what extent underlying thought processes are measured. And it is precisely these processes that appear to be important for functioning in society. A score on an intelligence test appears to influence a person’s identity. Is the concept of intelligence still useful to use?

Examples of how intelligence is defined

Because intelligence is not a concrete concept, everyone can give it their own interpretation based on intuition. These are often definitions where a feeling is what it could mean, but one does not know exactly what it means. An attempt is made to provide a description in vague words. This is evident, for example, from the following two definitions:

  • Intelligence is problem solving through abstract reasoning and learning (1)
  • Intelligence is the ability to process information well to solve problems


What do the above definitions mean?

The above definition raises a number of questions such as:

  • problem solving: what kind of problems?
  • abstract reasoning: what exactly does it mean? And is that better than concrete reasoning?
  • process information properly : what kind of information? What is good?

In fact, in these types of definitions one vague concept is replaced by another vague concept. It is a formulation at the intuitive level (2).

Intelligence classifies people on what basis?

Intelligence is a concept that attempts to classify people. In everyday interaction, someone is often called intelligent or stupid. It is unclear why. Even generalizations occur, often meant to be funny, but still. E.g. blondes are stupid. Tests are used to gain a grasp of the concept.

Intelligence classification by tests

There are numerous intelligence tests in circulation. E.g. Wisc, Wechsler, IDS. This test states that they can determine intelligence through an IQ (intelligence quotient). E.g. Achmed has an IQ of 110, Shullivan of 80, etc. Based on these figures, people are classified with an IQ score: low (below 90), medium (between 90-119), high (above 119).

How does such a test work?

The vague concept of intelligence is divided into sub-concepts devised by the test compiler for which assignments have been devised. Examples of such sub-concepts are: spatial ability, vocabulary, memory. The test compiler has devised assignments and subtests for this. The scores on these tests are combined and a total IQ is compiled from this. The total IQ indicates the degree of intelligence.

Do the different intelligence tests measure the same thing?

The various intelligence tests differ considerably in content and the scores also differ. (3) So they don’t measure the same IQ. An IQ score from a particular test only reflects the score on that test. It is therefore desirable to mention the name of the test. A purer definition of intelligence is therefore: intelligence is what the test measures (3).

What does an intelligence test actually measure?

An intelligence test measures results on the subtests. So if you are good at vocabulary you will score high there, but if you are bad at figure series you will score low there. Together your total IQ is determined. Does that say anything about your capabilities that lead to your intelligence?

What do intelligence tests measure too little or not at all?

An IQ test is about results, but the underlying thought processes are partly measured or not. This concerns processes such as planning, devising strategies, impulse control, making decisions, judging, empathic ability, etc. These are called executive functions . There is also another important factor such as perseverance. All these processes, which are part of the person as a whole, are important for success in life, whether at school or in a work situation. Older intelligence tests hardly measure these processes. Intelligence tests are based on a theoretical model, the so-called CHC model, which provides guidance for including certain cognitive functions in the test. Newer intelligence tests such as the Wechsler V also test some of these functions, but not all (4).

How can an incorrect intelligence determination be prevented?

An investigator will also have to look at the person. An intelligence test in itself does not say much. An example:

A student who is insecure or hyperactive can lose a lot of time completing a test assignment, causing him to score low because he does not finish within time. Another student also scores low, but this student lacks the planning ability to complete the assignment. Both students therefore score low, while the first student would be able to plan well if he had more time at his disposal. The second student does have planning problems. Planning, an important part of the thinking process, is not measured here (5).

By observing the actions and working attitude when taking a test and in other situations, a behavioral expert can find out why someone does poorly on a (sub)test, for example. An intelligence test would therefore best be administered individually so that the observer can gain insight into how the person being tested works. This may cause the person being tested to become nervous again.

How can an intelligence score influence someone’s identity?

An intelligence score shows how someone functions. It indicates something about his identity: who am I and what can I do? (6) If a score is low and there are consequences such as a job or school choice, it can influence how the person thinks he can develop further. For example, he or she does not apply for a nice job because it is thought to be too ambitious or chooses a lower education. Even in everyday conversations, the feeling can always arise: others are better.

What mainly determines success in identity?

We saw that an intelligence score in itself does not say much. It concerns the total person where three points appear to be more important (7):

  • perseverance,
  • setting goals
  • passion

There are examples of people who were able to achieve great things precisely because of this. These people have an identity of: I can do something, as long as I commit myself to it with passion. They do not need an intelligence test for this.


The concept of intelligence is not clearly defined. The definition is vague and difficult to measure. Moreover, tests differ in composition as well as the results. The best definition appears to be: intelligence is what an intelligence test measures. Intelligence tests also do not test or test too few underlying cognitive processes that influence the score. An achieved score appears to influence a person’s identity. Test researchers argue that an IQ score is in urgent need of modernization.(4) The question is whether the concept of intelligence would not be better abolished and replaced by a total profile of a person that can be determined both by behavioral experts and by the person himself and in consultation. composed.

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