Question
What does IQ stand for?
Short answer
IQ stands for intelligence quotient. The German psychologist William Stern proposed the term in 1912. Modern tests no longer compute a quotient: they report a deviation IQ, a standard score that compares you with people your own age on a scale with a mean of 100 and a standard deviation of 15.
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Where the name came from
Alfred Binet and Theodore Simon published the first practical intelligence test in 1905. In 1912 William Stern proposed the term “intelligence quotient”, and in 1916 Lewis Terman published the Stanford revision of Binet's test (Wikipedia: Intelligence quotient). A quotient is the result of a division, and the name reflects how early scores were built. Our short history of IQ tests covers this period.
Try one · Spatial Reasoning
Which option is the same shape, only rotated?
Tap the option you think is right, or show the answer.
Show the answer
Option 2 is the original figure turned a half turn.
How to solve it
- Pick a landmark: the marked cell or the end of the longest arm.
- Turn the figure in your head and watch where that landmark goes, and which side the other cells end up on.
- Turning the figure a half turn gives option 2.
- Each of the other options is a mirror image: flipping it over would match, but no turn does.
That was 1 puzzle. The full test has 25.
What an IQ is today
In 1939 David Wechsler introduced the deviation IQ with the Wechsler-Bellevue scale (Wikipedia: WAIS). Instead of a division, a deviation IQ compares your performance with a large sample of people your own age, then places you on a scale where that group averages 100 and the standard deviation is 15. Today's major tests, including the Wechsler scales and the Stanford-Binet, report scores this way (Wikipedia: Intelligence quotient).
So the word “quotient” is a leftover. A modern IQ of 115 does not mean anything was divided. It means you scored one standard deviation above the average for your age group, higher than about 84.1% of people. The deviation IQ entry in our glossary has the details.
Common misreadings of the name
- An IQ is not a percentage. 120 does not mean 120% of anything. See is an IQ score a percentage.
- An IQ is not a count of right answers. That is the raw score.
- An IQ is not a measure of everything a mind can do. It is a measurement of reasoning on one kind of test.
For how a modern score is built, read how IQ is calculated.
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale