Mental Age

Mental age (MA) is also known as an age norm, age equivalent score, or test age. It is defined as the age at which an individual performs on an intelligence test (Sax, 1997). For instance, a person who obtains the same number of points on an intelligence test as the average 8-year-old child is said to have a mental age of 8 years. A person's mental age does not necessarily correspond to his or her chronological age. Thus, a 7-year-old who obtains the same number of points as the average 11-year-old is said to have a mental age of 11 years.

The concept of mental age was introduced by Alfred Binet and Theodore Simon in 1908. Binet and Simon measured mental age by developing questions that would predict academic achievement. Earlier intelligence tests divided the mental age by the chronological age and multiplied this number by 100 in order to determine the intelligence quotient (IQ). Using this formula, a person's IQ was a person's mental age relative to his or her chronological age. Today, this formula is generally not used to obtain an IQ score because it does not take into account the “age of arrest,” which means that intelligence levels off in adulthood.

When performance on intelligence tests is examined throughout a person's lifetime, it is found that there is an increase in a person's scores throughout childhood and adolescence, a flattening effect when a person is in his or her teens or early twenties, and a decrease in performance after this time. Therefore, IQ tests today produce a mental ability score based on a person's performance relative to the performance of similar-age peers.

An additional problem with MA is that mental age units are not equal throughout the developmental period because mental growth does not occur at an equal rate across ages. For example, a child develops at a much higher rate between the ages of 2 and 3 years than between the ages of 11 and 12 years. For this reason, test scores vary more at different ages, thus making accurate interpretation of mental age scores difficult if not impossible. Another limitation of using mental age is that a global mental age does not accurately reflect the differences in a person's skills and abilities. It cannot tell you, for instance, that a person scored significantly better on tasks of a verbal nature, but performed poorly on nonverbal tasks. Despite the limitations of using mental age in interpreting test scores, mental age continues to be used because it is an interpretation that is widely understood by the general public.