What does mental age mean in psychology

Cognitive development and average IQ

A person's cognitive development is related to their age. Children get smarter every year. At the end of growth, the stabilizes cognitive development. At the age of 18, at best, one achieves slightly better results in an IQ test than at 16. If people stay healthy, their intelligence remains stable at least until they are 65.

It begins to decline around the age of 75: people then achieve poorer IQ results. This means that adults of all ages can be compared fairly well with one another.

The deviation IQ

Simon and Binet, the developers of the first intelligence tests, calculated the IQ using the formula “(mental age / chronological age) x 100”. This is of course very suitable for children. However, adults are not getting smarter every year, so this is not the right way to calculate IQ for them. Therefore, for children and adults, the so-called deviation IQ was used.

It compares a person's IQ test result with the average IQ of people of the same age. The average IQ is fixed at 100. If your score is over 100, you are smarter than the average person your age; if it is below that, you are (slightly) less intelligent than the average person your age.

That way, the degree of your cognitive development measured and expressed in the form of an IQ score. The average IQ in your age group is therefore always 100.

Read the next article on the Flynn Effect or take an IQ test.