The IQ Scale: What Does Your IQ Score Really Mean?

By: Alia Hoyt  | 
mad scientist
Does a high IQ mean a person is really smart? H. Armstrong Roberts/Getty Images

The term IQ, or Intelligence Quotient, generally describes a score on a test that rates the subject's cognitive ability as compared to the general population. IQ testing was formally named in 1912 by a psychologist named William Stern. The idea is that a person's average IQ score accurately represents their mental age in conjunction with their actual age.

Mensa gives the example that a 10-year-old with a mental age of 10, therefore, has an IQ score of 100. However, if the mental score is lower than the age, it drags the IQ score down. So, if the 10-year-old's mental age is 8, their score would only be 80. But, if their mental age was 12, their IQ test would reveal a score of 120. It's clear that modern IQ tests do take into account the age of a child when determining an IQ score, as children are graded relative to the population at their developmental level.


IQ Test Scores by the Numbers

Not surprisingly, IQ test scores are all about data. IQ tests use a standardized scale with 100 as the median or normal IQ score. Here are the IQ score ranges:

  • 130 and above: High IQ
  • 90-110 (median plus or minus 10): Average IQ
  • 80-90: Below Average IQ
  • 70 to 80: Borderline
  • Below 70: May indicate intellectual deficiency or mental retardation

Only 2 percent of people have what is considered to be a high IQ of 130 or greater. (Mensa only admits people whose IQ is 130 or higher.) Although that's extremely smart, some of the most brilliant minds of our time had IQs that were far higher. Albert Einstein and Stephen Hawking, for example, both boasted estimated genius IQ scores of 160. But even they don't come close to the alleged IQ of a math genius named Terence Tao, who claims an incredibly high IQ score of 220. To date, the highest score ever recorded belongs to an American writer named Marilyn vos Savant, who rates a whopping 228.


Sadly, IQ scores can be negatively affected by things that are often out of a developing child's control, like education access, nutrition and other such factors. Extremely low IQ scores are typically attributed to people with severe mental disabilities. The lowest IQ score is not documented, but obviously, the lowest score possible is zero.


What IQ Tests Measure

What is this cognitive ability being measured? Simply put, IQ tests are designed to measure your general ability to solve problems and understand concepts. This includes reasoning ability, problem-solving ability, ability to perceive relationships between things and ability to store and retrieve information. IQ tests measure this general intellectual ability in different ways. They may test:

  • spatial ability: the ability to visualize manipulation of shapes
  • mathematical ability: the ability to solve problems and use logic
  • language ability: This could include the ability to complete sentences or recognize words when letters have been rearranged or removed.
  • memory ability: the ability to recall things presented either visually or aurally

Questions in each of these categories test for a specific cognitive ability, but many psychologists hold that they also indicate general intellectual ability. Most people perform better on one type of question than on others, but experts have determined that for the most part people who excel in one category do similarly well in the other categories, and if someone does poorly in any one category, she also does poorly in the others.


Based on this, these experts theorize there is one general element of intellectual ability that determines other specific cognitive abilities. Ideally, an IQ test measures this general factor of intelligence, abbreviated as g. The best tests, therefore, like the Wechsler Adult Intelligence Scale or the Stanford-Binet test feature questions from many categories of intellectual ability so that the test isn't weighted toward one specific skill.


Can IQ Scores Be Increased?

a person holding a pencil takes a written test
Some people have got different IQ scores from retaking the same test. PeopleImages/Getty Images

Because IQ tests measure your ability to understand ideas and not the quantity of your knowledge, learning new information does not automatically increase your IQ score. Learning may exercise your mind, however, which could help you to develop greater cognitive skills, but scientists do not fully understand this relationship.

The connection between learning and mental ability is still largely unknown, as are the workings of the brain and the nature of intellectual ability. This does seem to depend more on genetic factors than on environmental factors, but most experts agree that environment plays some significant role in its development.


But can you increase your IQ score? There is some evidence that children develop higher ability if they receive better nurturing and diet as babies, and a higher degree of intellectual stimulation in preschool tends to boost children's IQ scores for a few years of elementary school but does not permanently increase IQ scores. Some people have even got different IQ scores from retaking the same test mutliple times.

For the most part, adult IQ scores don't significantly increase over time. There is evidence that maintaining an intellectually stimulating atmosphere (by learning new skills or solving puzzles, for example) boosts some cognitive ability, but these changes aren't permanent and do not have much effect on IQ scores. Another study found that exercise can increase the levels of brain-derived neurotrophic factor, a hormone necessary for new brain cells and connections. Continuing education may also boost IQ scores.


Criticisms of IQ Tests

IQ tests have been criticized for many reasons. One is that they don't take into account racial, class and cultural differences. This is important because IQ tests are used extensively to determine which public school children belong in classes for gifted students, and low-income and students of color are underrepresented in these classes in the U.S. A 2010 study looked at IQs from 108 countries and found African countries had lower IQ scores than other countries. But other researchers said the methods used for this study were unsystematic, "questionable and their results untrustworthy."

Another criticism is that your IQ doesn't really indicate how intelligent you are. IQ tests are only one imperfect method of measuring certain aspects of intellectual prowess. IQ tests don't measure creativity, social skills, wisdom, acquired abilities or a host of other things we consider to be aspects of intelligence. IQ tests also don't assess rational thinking, such as making the right decisions or dealing with a difficult client at work.


The value of IQ tests is that they measure general cognitive ability, which has been proven to be a fairly accurate indicator of intellectual potential. There is a high positive correlation between IQ and success in school and the workplace, but there are many, many cases where IQ and success do not coincide.

In fact, one study found that the kids who scored highest on IQ tests were the ones who were most motivated to do well on the test – and that a monetary reward made them try harder. In other words, an average IQ and determination could be more important for success in life than a high IQ and little motivation.