I’ve always heard that 100 is the “average” IQ, but is that specifically for the US, or is it a global average? And if 100 is average everywhere, how does that work—doesn’t that mean different countries would have different actual scores?
Also, I’ve seen some studies suggesting average IQ varies by country. If that’s true, where does the US actually fall? Is it above 100, below, or right at the standard average?
The US average is right around 100 by design—IQ tests are normed so that 100 is always the average for whatever population they’re standardized on. When tests are normed in the US, they set the average American score to 100. However, when comparing across countries using the same test, there are variations—the US typically scores around 98-100 depending on the study, which puts it slightly above global average but not at the top.
IQ tests are built so that 100 is the average in the country where they’re normed, so yes, the US average is 100. That said, international comparisons show some variation—countries like Singapore, Japan, and South Korea tend to score a bit higher (102-108), while the US hovers around 97-100 depending on the study. These differences are often attributed to factors like education quality, nutrition, and test-taking culture rather than innate differences.
International IQ comparisons are actually pretty controversial among Psychologists and should be taken with a grain of salt since a lot of cross-country studies don’t use truly representative samples. They might test students in urban areas with better schools, or use volunteer participants who aren’t representative of the whole population. This makes it hard to know if you’re really comparing countries or just comparing different subgroups.
I also read somewhere that things like nutrition, access to education, healthcare, and even test-taking familiarity are deeply tied to IQ scores. So when you see country-level differences, you’re often seeing the effects of these factors rather than something meaningful about the populations themselves. Because of these issues, a lot of psychologists are skeptical about ranking countries by IQ or drawing strong conclusions from those rankings since it’s much more complicated than it might appear on the scores.
@jkano While the generalizability is questionable, we must remember that IQ scores are based on relative rankings within a country. If a country’s sample is consistently drawn from its top students, and the resulting average IQ is, say, 105, it means that subgroup performed better than the average subgroup in other countries. The score itself may not be the true national average, but the ranking order of countries in the study might still hold if the sampling biases are similar across all nations.
@M.Evanta Do the scores remain stable over time once cultural factors are addressed? If these differences are truly due to modifiable factors like education quality and nutrition, then a country that implements aggressive, high-quality early childhood and K-12 reforms should see its national IQ mean rise to meet the higher-scoring nations within one or two generations.
Test creators arbitrarily set the average IQ for the population that the test is designed for. So, for tests like the RIOT that are normed on Americans, yes, the average is 100. But if we create a version of the RIOT for China, then we would set that group’s average to 100. We won’t be able to compare an American 100 to a Chinese 100 without some making sure that the tests are comparable. This is much harder than it sounds because cross-cultural testing is much more complicated than it appears. (One colleague of mine has written a book that’s 700 pages long about the topic.)
Without special analyses – the most popular of which is called a “test of measurement invariance” – it is difficult to make firm conclusions about score differences (individually or among groups) without these analyses. This is one reason why I am often skeptical of studies that report international IQs as being valid measures of international intelligence differences (see article here). It’s possible to make valid comparisons across countries, but you can’t just assume that; you have to demonstrate that the data really do meet the needed requirements to make those comparisons.
Some international comparisons with US data do use these procedures, but many do not. It’s a very frustrating aspect of being an intelligence researcher.