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Adults learn one new word a day

02 December 2010

Over the past three days we've gotten a fantastic response from people sharing this site on reddit and Facebook, with over 8,000 participations so far.

We've made two discoveries so far. The first is that, for native speakers age 18+, most people (74%) have a vocabulary size between 20,000 and 35,000 (13% below, and 13% above). Of course, this is for the specific subset of people who are Internet users and have taken our test so far.

Our second discovery is much more interesting, a statistic we haven't come across anywhere before. We calculated average vocabulary sizes for native English speakers for ages 15–32, which is the range of ages for which we have at least 100 respondents per year of birth, and discovered there is a remarkably linear progression from 23,303 words (age 15) to 29,330 words (age 32), which works out to an average increase of 355 words per year, or almost exactly one new word a day (0.97 words to be precise).

Now, this increase could be due to some kind of age-education bias among the test-takers, but we ran an analysis of average self-reported verbal SAT score per age as well in the same range, and it hovers around a constant 700 ±15 points, so the increase in vocabulary with age appears to be quite real—at least for people who originally scored quite well on their high school verbal SAT, who appear to be our main respondents so far.

This is actually quite fascinating—the fact that people don't simply stop learning once they're out of school, but that their vocabulary appears to be growing just as much at age 30 as it was at age 16.

And it leads to further questions: how much faster is vocabulary growth below age 15 (as it necessarily must be)? And to what extent, and when, does vocabulary growth start tapering off? More participation in the survey should tell us.