Question
Who invented the IQ test?
Short answer
Alfred Binet and Theodore Simon published the first practical intelligence test in France in 1905. William Stern coined the term intelligence quotient in 1912, Lewis Terman published the Stanford revision in 1916, and David Wechsler introduced the modern deviation IQ in 1939. No single person invented the IQ test as it exists today.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
The timeline
| Year | Event |
|---|---|
| 1904 | Charles Spearman proposes the general intelligence factor, g |
| 1905 | Alfred Binet and Theodore Simon publish the first practical intelligence test |
| 1912 | William Stern proposes the term “intelligence quotient” |
| 1916 | Lewis Terman publishes the Stanford revision |
| 1938 | Raven's Progressive Matrices first published |
| 1939 | David Wechsler introduces the deviation IQ with the Wechsler-Bellevue scale |
| 2003 | Stanford-Binet Fifth Edition (SB5) |
| 2008, 2024 | WAIS-IV, then WAIS-5 |
Sources: (Wikipedia: Intelligence quotient), (Wikipedia: g factor), (Wikipedia: Raven's Progressive Matrices), (Wikipedia: WAIS), (Wikipedia: Stanford-Binet).
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a large outlined square, with small solid shapes: a triangle at the top-right corner and a triangle at the bottom-right corner (option 3).
How to solve it
- Compare the first two panels and name exactly what changed.
- The main shape and the small shapes swap forms: the main shape takes the form of the small ones, and the small ones take the form of the main shape.
- Nothing else changes.
- Apply the same change to the third panel: a large outlined triangle pointing up, with small solid shapes: a square at the top-right corner and a square at the bottom-right corner.
- So the missing panel shows a large outlined square, with small solid shapes: a triangle at the top-right corner and a triangle at the bottom-right corner.
That was 1 puzzle. The full test has 25.
Why the answer has several names
Binet and Simon built the first test people could actually use. Stern gave the score its name. Terman's Stanford revision spread the idea widely. Wechsler changed how the score is calculated, comparing each person with their own age group on a scale with mean 100 and standard deviation 15, and that deviation IQ is what modern tests report (Wikipedia: WAIS). So if you mean the idea of an intelligence test, the answer is Binet and Simon. If you mean the IQ score you would get today, the answer is closer to Wechsler.
Nonverbal tests
John C. Raven developed his Progressive Matrices in the 1930s as a test of reasoning without words (Wikipedia: Raven's Progressive Matrices). Matrix puzzles in that tradition are still the core of nonverbal testing, including on IQ Octopus. You can try free examples in the matrix puzzle library.
For more context on each step, read the history of IQ tests or what IQ stands for.
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale
- Stanford-Binet Intelligence Scales. Wikipedia. en.wikipedia.org/wiki/Stanford%E2%80%93Binet_Intelligence_Scales
- Raven's Progressive Matrices. Wikipedia. en.wikipedia.org/wiki/Raven%27s_Progressive_Matrices
- g factor (psychometrics). Wikipedia. en.wikipedia.org/wiki/G_factor_(psychometrics)