The Importance of IQ

So what is IQ?

The idea behind IQ (intelligence quotient) sprang from the observation that, as children get older they can do increasingly more difficult tasks, solve increasingly difficult problems and learn increasingly difficult concepts. Culminating in the theory that each individual possess a mental age that could be measured against the norm. Therefore, IQ attempts to calculate how much someone's intelligence (as measured by an intelligence test) compares with that of other people of the same age.

How then do we know if a person is above average intelligent? The answer to this question is surprisingly simple, he or she would have an IQ that was above 100. Calculating IQ is actually very simple.  Each person has a true age which is known as there chronological age (CA), when they complete an intelligence test, this gives a figure of their metal age (MA). The two figures are then divided by each other and multiplied by 100. The resulting score is that person's IQ.

The mathematics look like this: -(MA)/(CA) x 100 = IQ

Let us place some numbers into this equation. Suppose we designed a test containing 12 problems each valued at 1 point. We knew on average that a 6 year old could be expected to solve the first 6 problems, an 8 year old the first 8 problems and that a 10 year old could be expected to solve the first 10 problems. Now let us assume that the first test revealed that the 10 year old actually only solved 8. Their chronological age (CA) is known to be 10, whereas their mental age (MA) would be 8 and consequently below what we expected.

This gives us: -(8)/(10) x 100 = 80 So the person has an IQ of 80.

Let us suppose that in the next test a 6 year old solved 8 of the problems. Their chronological age (CA) is known to be 6 whereas their mental age (MA) would be 8 and consequently above what we expected.

This gives us: -(8)/(6) x 100 = 133 So the person has an IQ of 133.

The idea then is that 'IQ's over 100 represent bright children, 'IQ's below 100 represent the children who are not so bright. Therefore, the average child would by definition have an IQ of about 100.

Testing children and teenagers using this method works well up to the age of about 18. However, a different method is needed to test adults. The (MA) divided (CA) formula is not really an appropriate test for adults because it is based on the linear growth of mental age.  In other words, we become increasingly smarter year after year until the day we die. However, this is generally not considered to be the case. It is in fact believed that there is little or no growth in mental age after a person reaches about 20 years of age.  Consequently a different formula is used to calculate the IQ of adults. This gives a similar result to the one used for children but is considered to give a more accurate result.

The test for adults is based on the natural distribution of IQs in the population. It should be stressed that in describing the methods of IQ testing, that this can in no way be considered as an endorsement of their value or use. Furthermore, although it is accepted that IQ tests do measure something, what is actually being measured is unknown.