mental age

mental age, intelligence test score, expressed as the chronological age for which a given level of performance is average or typical. An individual’s mental age is then divided by his chronological age and multiplied by 100, yielding an intelligence quotient (IQ). Thus, a subject whose mental and chronological ages are identical has an IQ of 100, or average intelligence. However, if a 10-year-old has a mental age of 13, his IQ is 130, well above...