Intelligence Measurements : Intelligence Quotient And Mental Age

• History of Modern Intelligence Measurement

Modern method of measuring intelligence dates back to 1875, when scholars such as Cattell and Galton recognized individual differences. In 1879, Williams Wundt established first psychological laboratory in Leipzig, Germany.

In France in year 1905, Alfred Binet wanted to find out why examination results of students are falling in France? He wanted to know that what is ability that leads to success or failure? So he created first intelligence test with 30 questions.

Binet first gave the concept of finding mental age. Terman, research scholar at Stanford University, modified Binet IQ test and named it Stanford-Binet Intelligence Test. In 1937, Terman, with help of Merril, revised it again and named it 'Terman - Merrill Scale'. Burt made test on this basis.

• Concept of Mental Age

Mental age is determined on basis of intelligence tests, that is, on basis of how correctly a child can solve questions of intelligence test, his mental age is known.

In fact, relationship between child's mental development and his physical age is basis of measurement of intelligence. mental age of a child of any particular age should be same as actual age of that child - it is not so.

* How to Find Mental Age

If a 10 year old boy can solve intelligence test which is designed for 12 year old boy, then his mental age will be 12 years. Mental age means age which is determined by intelligence or mental test.

Binet gave idea of ​​finding mental age, in that had possibility of errors in calculation of mental age. So psychologists gave idea of ​​'Intelligence Quotient'.

• What is Intelligence Quotient

Intelligence Quotient is related to mental age of child. First, mental age of child is determined on basis of mental examination. After that it is converted into intelligence quotient. In 1908, Binet gave the first idea of ​​mental age.

Binet's mental age of meaning is, age that is attained by average of results of intelligence or mental tests. Terman accepted Binet's idea of ​​mental age and initially used the following formula to calculate IQ.

Intelligence Quotient formula = Mental Age / Chronological Age.

The biggest flaw in this formula was that intelligence often came in imperfect numbers i.e. decimals. To remove this defect, Stern calculated intelligence by following formula.

Intelligence Quotient Formula

Intelligence Quotient (IQ) = Mental Age / Chronological Age×100

How to find IQ?

Example : If a child's chronological age is 12 years and he solves same number of questions as a 15 year old boy, then according to formula his IQ will be as follows -

I.Q. = M.A. 15/C.A. 12 ×100 = 125 

That is, I.Q. = 125.

Thus, IQ is a ratio between chronological age of a child and his mental age, which is multiplied by 100 and converted into units of a particular scale. The intelligence quotient of a child does not remain same throughout his life.

Development of mental age is together with chronological age. IQ has a specific distribution of its own. Terman and Merrill were first to divide IQ using experiments on students. Later Kamath found this distribution according to conditions of India which is as follows.

• Classification of IQ According to Kamath

 Intelligence QuotientCategory%
130 to 139.5Extraordinary3.5
120 to 129.5Very Superior9
110 to 119.5Superior15
90 to 109.5Normal 42
80 to 89.5Backward15
70 to 79.5Very Backward9
60 to 69.5Border Line3.5
50 to 59.5Morons2.5
40 to 49.5Feeble.5
Under 30Idiot.5

• Classification of IQ According to Terman : Intelligence Quotient Scale

 Intelligence QuotientCategory
Under 25Idiots
25 to 50Imbeciles
50 to 70Morons
70 to 80Feeble minded
80 to 90Dull
90 to 100Average
100 to 125Superior
125 to 140Very Superior

Other scholars also presented their other similar classifications, but one common thing is clear from all these classifications that the higher intelligence quotient, the more capable he will be.

Intelligence Measurements, Intelligence Quotient, Mental Age

• Stability of Intelligence Quotient

It is often believed that as the age of child increases, his mental development also increases in same way, but this does not happen throughout his life.

In fact, in initial years, mental development is very rapid, after that its pace slows down. Between 15 years and 18 years, full development of an adult is completed and mental development remains stable till age of about 40 years.

Psychologists believe that although child's mental development keeps on changing, yet his IQ remains stable, it does not change. Some psychologists also believe that there is change in the intelligence quotient due to many reasons.

Basis of most of research studies, it has been concluded that there is change in intelligence quotient according to time and environment, although this change is not very much. It is belief of most psychologists that IQ is usually constant.

It is clear from above description that extent of Intelligence Quotient determines Heredity but environment presents possibilities of its full development and with age there is little change in the IQ.

Also Read :

1. Intelligence : Meaning And Definitions, Characteristics And Types

2. Theories of Intelligence

3. Types of Intelligence Test : Individual And Group