What does the term "mental age" in IQ testing refer to?

The term "mental age" in IQ testing refers specifically to the age level of intellectual performance, which is determined by comparing an individual's performance on an intelligence test to the average performance of different age groups. This concept, developed by Alfred Binet, was intended to assess a child's cognitive abilities relative to their peers. For example, if a ten-year-old child performs at a level typically associated with a twelve-year-old, their mental age would be considered twelve, even if their chronological age remains ten. This measure provides a way to understand cognitive development and intellect more flexibly than simply looking at the person's age in years.