The Concept of Chronological Age (CA), Mental Age (MA),Basal Age (BA) and Intelligence Quotient (IQ)

 The Concept of CA, MA, BA and IQ

It is a matter of fact that the function of psychological tests is to measure individual differences. But the ideas of intelligence test was first mooted by the French Psychologist, Alfred Binet to measure intelligence and before that attempts were made to measure intelligence through unscientific or crude manner. Now intelligence test is used in a variety of situations and provides a single score such as I.Q. indicating individuals general intellectual level.

Before we make an attempt to assess the intelligence of an individual the following basic concepts must be understood. These are as follows.

(1) Chronological Age:

It refers to the actual age of an individual or his/her date of birth. It is symbolically called as CA.

(2) Mental Age

The concept of Mental age was introduced by Alfred Binet in the year 1908. MA merely indicates the level of development which a child has reached at a given age. It shows the mental level but it does not tell us how bright the child is. It gives us an idea whether the child is advanced or retarded or average when compared to normal children of his/her age.

The concept of MA has made the interpretation of Intelligence easier. If the MA of a child is equal to his chronological age then he is normal. When he is greater than the CA, he is advanced and less than the CA is retarded. It is otherwise called the mental maturity achieved by the child at some particular age or MA is a kind of score which gives an idea of about the intellectual development of the child. Maximum mental age of a person is 19 or 20. The procedure of calculation of mental age is as follows. A child's mental age is calculated by adding the basal age and the credits (in terms of months) obtained by him in subsequent levels.

Suppose a child takes a test of intelligence and there are six sub-tests in the test. Success in passing one sub-test means a credit of 2 months and passes all the six sub-tests means a credit of 12 months. Take for example a five year child and his success and credits earned at various levels are given below.

1. Passed all tasks at 5 years level   -  5 years (Basal age) 

2. Passed 4 out of 6 tasks at 6 years  - 8 months credit level

                                                               (4 x 2)

3. Passed 4 out of 6 tasks at 7 year  -  4 months credit level

                                                              (2 x 2)

4. Failed all tasks at 8 years level    -  0 months credit

-------------------------------------------------------------------

               MA Total: 5yrs 12 months = 6 years

Thus, the child MA would be 6 years though he is chronologically 5 years old. Thus mental age basal age + partial credit or fractional credit for the items up to the terminal age.

3. Basal Age

Basal age is that age of the child where he or she can solve all questions in a given test. It is the basal age which helps in the calculation of mental age. Suppose a child is 5 year age (CA). He solves all questions in a given test meant for a child of 6 and 7 years and solves only one question out of 6 questions in a test of 8 years and unable to solve any of the questions of 9 years. Thus his basal age is 7 years 2 months though his CA is 5 years.

4. The Concept of I.Q.

Intelligence Quotient is the ratio between mental age and chronological age multiplied by 100. Symbolically it is called I.Q. I.Q. is calculated with the formula, i.e., I.Q.= MA/CA x 100. In the year 1916 Stern gave us this concept to CA know the degree of brightness or dullness. It is a method of defining relative intelligence because IQ is independent of the scores which he happens to make at a particular age.

It has been observed by Terman in 1916 revision test that individual mental age increases along with his chronological age up to 16 years. Though the CA goes on increasing yet for the purpose of calculation of IQ, chronological age may be taken as 16 years. Again in the 1937 scale, Terman assumed that for computing IQ, the CA for all adults was taken as 16. Since mental growth continues beyond the age 16, the highest chronological age included in the IQ tables is 18, in the 1960 scales. Accordingly the CA of any adult taking the test is taken as 18 for computing the IQ. Thus Intelligence Quotient in fact a ratio of the physical and the mental age of the child or ratio of mental growth or the rate of mental growth of a child.

Limitations of 1.Q.

1. IQs on one test are not comparable to those obtained on another test. 

2. IQ in case of adults are only hypothetical and are open to doubt. 

3. IQ. tells the rate of maturity but two children having an I.Q. of 120. may not be equally mature. 

4. The difference between an I.Q. of 70 and 80 is not the same as the difference between an I.Q. of 110 and 120.