What's an IQ? Questions About IQ Testing

Answers to common questions about IQ and IQ Testing

IQ tests
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What does IQ stand for?
IQ is an abbreviation for the term intelligence quotient. The work of Howard Gardner, a professor at Harvard University, has introduced the widely-accepted theory of multiple intelligences (or abilities as some critics argue). These intelligences are: Spatial; Linguistic; Logical-mathematical; Bodily-kinesthetic; Musical; Interpersonal; Intrapersonal and Naturalistic.

According Linda S. Gottfredson, one of the foremost champions of IQ as a single measure, Gardner’s different types of intelligences all rely on a singular type of intelligence, referred to as general intelligence or the g-factor.



What is an IQ?
In its most simple form, an IQ is a number from 0 to 200+ that rates a person’s cognitive ability in comparison to the general population. Children’s IQ scores also take age into account, so their IQ score is in comparison to their same-age peers as opposed to the population as a whole.

How is IQ determined?
The formula for determining IQ can best be described as:

IQ= 100 x Mental Age /Chronological Age

While determining chronological age simply relies on a child’s birth-date, mental age is determined by educational tests. While the standard test for IQ used to be the Standford-Binet, now the most widely used and accepted tests are the Wechsler Scales.  

There are two versions for children: Wechsler Preschool and Primary Scale of Intelligence, 3rd ed. and the Wechsler Intelligence Scale for Children, 4th ed. The WPPSI-III is used for children up to 5 years, 11 months of age and the WISC-IV is for children ages 6 to sixteen.



What do the numbers mean?
IQ scores are often represented as a bell curve, with 100 being right in the middle of the curve. However, since most IQ testing has a standard deviation of 15 points in either direction, a score between 85 and 115 denotes average intelligence.  

Above 130 typically denotes exceptional intelligence, while a score of 70 or below falls into the range of mental retardation.

It’s important to note that mental retardation can range from mild to moderate, so an IQ score doesn’t always tell the whole story. The same can be said for average or above intelligence, too.

What’s a bell curve?
A bell curve is named for the made when normal distribution is mapped out. Basically, a bell curve is a graph that slopes upward into a rounded mountain-like shape and then slopes downward on the other side. The middle of the mound is the mean value (the average),to the left are the numbers that fall on the low side of average and to the right are the numbers that fall on the high side. The shape clearly illustrates that the majority falls in the middle.

What do IQ tests measure?
The end result of an IG test is the g-factor, or the number that gives a sense of what a person’s ability is to learn. Unlike achievement tests  IQ tests don’t measure knowledge, they measure problem-solving skills and how well a person can understand things. The Weschler Scales measure this by testing four main indexes:

  • Verbal Comprehension: Measures a  child’s understanding of language, including vocabulary,auditory memory and following verbal directions.
  • Perceptual Reasoning:  Measures a child’s ability to look at a problem, use visual -motor and spatial skills to organize and test a solution.  
  • Working Memory: At one point known as Freedom from Distractibility, this measures a child’s ability to take in, store and memorize new information and then concentrate to use that information to complete a task or other problem-solving process.
  • Processing Speed: Measures how quickly and accurately a child is able to scan information presented visually and see differences between or put that information in some sort of order.

How stable is an IQ score and can it change?
The stability of an IQ score relies on many factors. For the most part, the older a child is when the test is given, the more reliable the score and the more likely it will stay the same over time.

When IQ tests are given at the preschool level, they are much less predictive of a child’s IQ at the age of 10, for example. In that regard, yes, an IQ score can change over time. An IQ score is also somewhat dependent on a child’s ability to participate in the testing, either because of refusal or developmental ability to understand what is being asked of her.

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