Mental Age

A scale used to correlate intelligence to the typical changes that occur as a child matures.

French psychologist and educator Alfred Binet theorized that a child who appears to have limited mental abilities is able to perform on a level characteristic of younger children; conversely, a child who appears to be gifted is able to perform on the level of older children. In 1905 Binet, in collaboration with Thèophile Simon, developed a scale on which mental age could be compared to the chronological age. Thus, a bright child's mental age is higher than his or her chronological age.

In 1916, Lewis Terman, a psychologist at Stanford University, devised an intelligence test based on Binet's work (referred to today as the Stanford-Binet Intelligence Scale) and was administered to assess American school children. Terman maintained the concept of mental age in devising his formula for calculating the intelligence quotient (IQ). The formula is IQ = mental age/chronological age multiplied by 100. Thus if the child's mental age equals her chronological age, her IQ will equal 100.