A ten-year-old child may in some ways function like a three-year-old child hence making the mental age theory a controversial concept.

Just like Alfred Binet, Lewis Terman and David Wechsler are considered as some of the key contributors in intelligence research and testing who greatly contributed to the field of psychology with respect to human intelligence. Terman revised and expanded Binet’s test to an extent that it was published in 1916 at Stanford. He incorporated new scoring scheme and introduced the concept of Intelligence Quotient (IQ) which referred to child’s mental age divided by chronological age, multiplied by 100 (IQ = mental age/chronological age x100). Lewis study claimed that the stereotypical view of gifted children is that they are sickly, bookwormish, and socially inept. Initially, the study involved 1500 children who had normal IQ of 150 in comparison to standard subjects and the findings were that the children were above average in height/weight, physical health, emotional adjustment, mental health and social maturity.

The Wechsler Adult Intelligence Scale (WAIS-IV and WISC-IV) refers to an intelligence test that was developed to quantify human intelligence in adults and in adolescents (Russell, Norvig & Davis, 2010). Wechsler alleged that intelligence comprised of diverse perceptual abilities rather than one broad intelligence factor. His test comprised of many ideas that were initially espoused by Binet but unlike Binet, Wechsler provided a profile of the test taker’s overall weaknesses and strengths. The main strength of this approach is the fact that the patterns of scores may also provide worthwhile information. For instance, scoring high in some areas but low in the rest might depict the existence of a particular learning disability. WAIS also gives the overall scores though it calculates the numbers using a different concept.