Mental Age

Mental age is a central concept in the study of intelligence measurement. Jerome Sattler defined mental age as “the degree of general mental ability possessed by the average child of a chronological age corresponding to the MA score” (p. 172). As an example, a child assessed with a mental age of 9 is viewed as having the general mental ability of an average 9-year-old child.

From the perspective of intelligence measurement, each individual has two ages: a chronological age that is the number of years that the individual has been alive, and a mental age that is the chronological age of persons for which the test performance of the individual is the average test performance.

The mental age and the chronological age of an individual need not be the same. For example, if the mental age of an individual is greater than the chronological age of the individual, then one can infer that the individual has above-average intelligence or higher mental ability.

The mental age and the chronological age for an individual are used to determine the ratio IQ (intelligence quotient) of the individual. To compute the ratio IQ, one divides the mental age of an individual by the chronological age of the same individual and then multiplies that ratio by 100. For example, if a child has a mental age of 12 and a chronological age of 10, then the ratio IQ for that 10-year-old child is 120 (i.e., 12/10 × 100 = 120).

The ratio IQ was the measure of intelligence used in the 1916 and 1937 versions of the Stanford–Binet Intelligence Scale and on other tests of mental ability. The deviation IQ replaced the ratio IQ as the measure of intelligence used in subsequent measures of intelligence. The deviation IQ reflects the location of the test performance of an individual in a distribution of the test performances of other persons with the same chronological age as the individual, with the mean deviation IQ being typically equal to 100. For example, if an individual has a test performance that is less than the mean test performance for same-age peers, then the individual will have a deviation IQ less than100. Neither the dated measure of ratio IQ nor the more contemporary measure of deviation IQ consistently provides concrete information as to the reasoning skills of individuals.

The mental age score may also be termed the age-equivalent score according to Sattler. The mental age score for an individual provides information as to what age group is most closely associated with the individual from the perspective of mental ability. As an example, a 12-year-old child with a mental age score of 14 indicates that the 12-year-old child has [Page 660]a mental ability more typical of 14-year-old children than of 12-year-old children.

Sattler noted that mental age scores have certain limitations. First, differences in mental age do not reflect the same differences in mental ability across the age spectrum. For example, the difference in mental ability between a mental age score of 5 and a mental age score of 2 tends to be greater than the difference in mental ability between a mental age score of 15 and a mental age score of 12. Second, the same mental age may reflect different capabilities for different individuals. For example, two children both with the mental age score of 12 may have answered different test items correctly.

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