What's the Difference Between Mental Age and Chronological Age?

In the early days of ause of intelligence tests, lewis turman drew on work of german psychologist william sterne. He helped popularize the notion of something called an intelligence quotient - what we now know to day as icue. Mackintosh was one of the most respected researchers in the field of intelligence but he was also genuinely open minded and responsive and curious. But his personality and his demeanour and everything about him, a just signalled a pure, pure love of science.