What Is IQ? A Simple Guide to Intelligence Scores

IQ stands for intelligence quotient. It is a number that compares a person's performance on a set of reasoning tasks with the performance of other people in the same age group. The idea goes back to the early 1900s, when psychologists such as Alfred Binet developed tests to help identify children who needed extra support in school.

How IQ scores are calculated

Modern IQ tests are standardized. This means they are given to a large and carefully chosen sample of people, and the results are used to set the average score at 100. Scores are then spread out in a bell-shaped curve with a standard deviation of 15 on most major tests. About two out of three people score between 85 and 115, and roughly 95 percent score between 70 and 130.

What IQ tests measure

• Logical reasoning: spotting rules and drawing conclusions.
• Pattern recognition: seeing the structure in number, letter or shape sequences.
• Verbal reasoning: understanding relationships between words and ideas.
• Working memory: holding and using information for a short time.
• Processing speed: how quickly simple mental tasks are completed.

What IQ tests do not measure

IQ does not measure creativity, emotional intelligence, curiosity, motivation, kindness or practical skills. Many successful people have an average IQ and excel because of persistence, social ability and good habits. A single score on one day is only a snapshot, and it can be affected by sleep, stress, mood and how familiar you are with the question style.

Online IQ tests versus professional tests

Professional tests such as the Wechsler scales or the Stanford-Binet are given one-on-one by a trained psychologist, take one to two hours and are compared with large standardization samples. Short online tests, including ours, are useful for fun and practice but cannot give an official score. If you need a real assessment for educational, medical or employment reasons, speak to a licensed professional.

Can your IQ change?

Adult IQ scores are fairly stable, but performance on reasoning tasks can improve with practice, good sleep, regular exercise and learning new skills. Familiarity with puzzle types is one of the easiest ways to raise your test performance. See our guide on ways to sharpen your thinking.