Brief notes on Intelligence Quotient (IQ)


Intelligence quotient is just a number; it was devised in 1912 by a German Psychologist, William Stern (1871-1938). It is an age-related measure of intelligence level. I.Q. is determined by child’s mental age divided by chronological age multiplied by 100.

I.Q. (Intelligence Quotient) = MA/CA x 100

The number 100 is used as a multiplier to avoid the decimal point. When the M.A. equals the C.A., the I.Q. is equal to 100. When the M.A. is less than the C.A., the I.Q. is less than 100. If the M.A. is above the C.A., the I.Q. becomes more than 100.


The test of intelligence developed by Binet had the following four characteristics. First, the score on his newly developed test was an assessment of the current performance, and not a measure of the inherited attributes. Second, his test scores were to be used to identify weak children,” who needed special help, and there should be no stigma attached to them for their weakness.

Third, he believed that intelligence can be influenced by training and opportunity, and he tried to identify the areas in which special education can benefit the performance of these children. And fourth, he did not develop a theory of intelligence; he developed his test empirically on the basis of how children’s performances can be observed.

The test originally developed by Binet was revised several times in his country and in England. Terman, a Professor at the Stanford University, revised Binet’s test in 1916, which was known as the Stanford – Binet test of Intelligence. This test underwent further revisions in 1937, 1960, and 1972. The present Stanford – Binet test has a wide variety of verbal and nonverbal items.

For example, for a six-year-old child, the verbal task in the test is to define at least six words, such as “envelope”, “orange” etc. His/her nonverbal tasks consist of tracing a path through a maze. An adult would be required to define such words as “regard”, “disproportionate”, and to explain several proverbs. The test also consists of subtle thinking to differentiate between “laziness” and “idleness”. The Stanford-Binet’s latest tests for adults have four components such as Verbal reasoning, Quantitative reasoning, Abstract reasoning, and Short-Term memory


Binet’s measurement of intelligence is found to approximate a normal distribution. This type of distribution is symmetrical with a majority of cases falling in the middle of the range of scores and a few scores falling at the curve.

The Stanford-Binet test is popular and most widely used test intelligence. It is considered to be advantageous compared to that developed by Galton or Cattell. This is because, contrary to sensory, perceptual, and motor processes only, the Stanford-Binet test captures complex mental processes such as memory, imagery, comprehension, and judgment.

The following table shows the classification of people on the basis of their IQs.


Description of IQ Level

Percentage in Each Group

Above 139

Very Superior






High average






Low average



Border line


Below 70

Mentally retarded


The Wechsler Scales

In addition to the Stanford-Binet test, the Wechsler scalesĀ  are most widely used intelligence tests. These scales were developed by David Wechsler of the me Hospital in New York. There are three scales: the wechsler Adult Intelligence Scale-Revised (WAIS- le Wechsler Intelligence Scale for Children Revised (WISC-R), and the Wechsler Preschool and primary Scale of Intelligence (WPPSI).

These scales gone through successive revisions. Recently, of these scales were revised in 1981. The wechsler scales provide an overall IQ score, and also I IQ and non-verbal IQ scores. The separate verbal non-verbal scores help the tester to see quickly areas of mental performance in which the individual below average, average, and above average.

The WAIS-R consists of six verbal and five non-verbal subtests. Some of the verbal subtests are Vocabulary, Comprehension, Arithmetic, Simile and Digit Span. As an example, in Similarities, the person is required to state how two things are alike.

In the subtest of Digit Span, the person is as repeat a series of digits in the same order as presented by the examine non-verbal or the performance subtests of the WAIS-R include the subtests of Block Design, Digit Symbol, Picture Arrangement, Picture Completion Object Assembly. The WAIS-R is designed for adults over 18 yean Wechsler Scales are highly reliable and valid.

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