Understanding the Classification of IQ Range

Words and phrases like IQ, IQ chart, IQ score and IQ range are in frequent use; but are they understood and did you know the difference between all of these? Let’s start by following the measurement of Intelligence Quotient (IQ) to comprehend the difference between IQ range, chart, and score.

Understanding Intelligence Quotient

What is intelligence?

There are many different kinds of intelligence, each connoting a varying ability of the mind. However, when collectively speaking, intelligence is the mind’s ability to comprehend a situation, to deal with that situation, to derive conclusions from the situation and the ability to draw the solution from a problem existing in the situation.

Every human is different from the other based on various characteristic differences. One of these is the capability of his brain. To be right placed in groups of matching intelligence levels, psychologists have been looking for ways of aptly measuring this intelligence of the human mind. It led to the development of intelligence quotient and the IQ range.

Relationship Between Intelligence Quotient and the IQ Scale

The intelligence quotient is a score, measured in numbers, which is yielded after administering specific approved intelligence tests to the participants. These ratings are then tallied with the intelligence quotient scale as devised by Wechsler or Lewis Terman, the originators of intelligent quotient scale, after which the intelligence level of the individual is determined.

Surprisingly, on both scales, the score of 100 denotes average intelligence for a particular age. So, the average rating or the mean intelligence quotient for both scales is 100. This count then gradually decreases on both sides of the scale on which one end connotes mentally impaired, developmentally disabled individuals, while the score on the opposite end suggests an unusually gifted or genius individual. 

The intelligence scale starts somewhere from 36-40 and goes up till 160-164, with 100 coming in the center as mentioned earlier. The intelligence chart or graph visually interprets these scores making a bell-shaped curved graph and is mostly compatible with individuals of all ages when they are tested with the appropriate tests. By observing this intelligence chart or graph, one can make out the IQ range showing the different intelligence levels. Let’s look at these scales in detail to understand where each is placed after being tested with the intelligence tests.

Standard Deviation on the Intelligence Chart

With the mean score coming in the center of the graph, the spread of the rest of the scores is equal on both sides creating a standard distribution curve. So, about 2/3 of the total scores collected will fall within the first standard deviation from the mean forming the range of most individuals sharing almost the same intelligence level. Around 95% of the total scores collected will make up two standard deviations from the center. 

History of IQ Range Classifications

Over the past many decades, various classifications of IQ range have been introduced. Lewis Terman’s ranking of the IQ came first and is as follows,

·         Score of 140 and Above

Individuals in this range are classified as a genius or near genius.

·         Score Between 120 and 140

Individuals in this range are classified as having very superior levels of intelligence.

·         Score Between 110 and 120

People who are grouped in this range are classified as having a superior form of intelligence.

·         Score Between 90 and 110

Individuals here said to have a normal or average level of intelligence amongst their age mates.

·         Score Between 80 and 90

In this group, the individuals are considered as having a dull mind.

·         Score Between 70 and 80

Individuals in this category have a borderline deficiency of intelligence.

·         Score Below 70

According to this classification, individuals are feeble-minded.

Now let’s take a look at the IQ range as classified by Wechsler later on.

·         Score of 128 and Above

Individuals have very superior intelligence

·         Score Between 120 and 127

People in this group have superior intelligence.

·         Score Between 111 and 119

Individuals in this category are normally bright.

·         Score Between 91 and 110

Individuals have average intelligence

·         Score Between 80 and 90

Individuals are classified as dull normal.

·         Score Between 66 and 79

People here have a borderline deficiency.

·         Score Below 65

People have defective intelligence levels.

IQ Range of Mental Deficiency

Earlier on there was a fine classification of mental deficiency which is now obsolete, and individuals below an IQ score of 70 are just considered mentally retarded.

A.  Earlier Classification

a.   70 to 80: borderline deficiency

b.   50 to 69: moron

c.   20 to 49: Imbecile

d.   20 or Below: Idiot

B.  Current Classification

a.   50 to 69: Mild

b.   35 to 49: Moderate

c.   20 to 34: Severe

d.   20 or Below: Profound


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