In 1905, Alfred Binet and Theodore Simon made the first successful attempt to measure intelligence. Later in 1908, they gave the concepts of:
- Mental Age or MA– this is the measure of a person’s intellectual development relative to people of his/her age group.
- Chronological Age or CA– this is the biological age of the individual from birth.
- For a bright child, the MA is more than his/her CA. whereas, for a dull child, the MA is below the CA. retardation was explained by Binet and Simon as being 2 mental ages below the chronological age.
- In 1912, William Stern, a well-known German psychologist, introduced the concept of Intelligence Quotient or I.Q. It refers to the mental age divided by the chronological age and then divided by 100.
- 100 acts as the multiplier in order to avoid the decimal point. When MA equals the CA then the I.Q. equals 100. If MA is more than 100 then it means the I.Q. is also above 100. If the MA is lower than 100 then the I.Q. is lower than 100.