What is IQ?
IQ (intelligence quotient) is a score that describes how someone's reasoning and problem-solving abilities compare with those of other people their age.
A short history
The first practical intelligence test was created by Alfred Binet and Théodore Simon in France in 1905 to identify children who needed extra support at school. The term “intelligence quotient” comes from William Stern, who divided a child's “mental age” by their real age and multiplied by 100.
Modern tests no longer use that formula. Today an IQ is a deviation score: your performance compared with a large reference group of people your age, placed on a scale where the average is 100.
What IQ tests measure
Most modern tests are built on the Cattell–Horn–Carroll (CHC) model, which describes intelligence as a general factor (often called g) plus several broad abilities. IQ Atlas measures six of them: fluid reasoning (pattern recognition and logic), quantitative reasoning, visual-spatial processing, working memory and processing speed.
What IQ predicts, and what it doesn't
IQ is one of the most studied measures in psychology. It predicts school performance, job training success and, more weakly, job performance and income. But it doesn't measure creativity, character, motivation, emotional skills or wisdom, and a single score always comes with a margin of error.
Is IQ fixed?
IQ is fairly stable in adults, but not set in stone. Education raises measured IQ, and average scores rose by roughly 3 points per decade in many countries during the 20th century (the Flynn effect). See can you increase your IQ?
Frequently asked questions
What does IQ stand for?
Intelligence quotient. The name comes from an early formula that divided mental age by real age; modern tests compare you with people your own age instead.
What is a normal IQ?
By design the average is 100, and about two thirds of people score between 85 and 115.