(x, say) is derived such that the individual's score equates to the average score at age x.

However, mental age depends on what kind of intelligence is measured. For instance, a child's intellectual age can be average for their actual age, but the same child's emotional intelligence can be immature for their physical age. Psychologists often remark that girls are more emotionally mature than boys at around the age of puberty. Also, a six-year-old child intellectually gifted