What Is Lydia Sebastian's IQ? The 12-Year-Old's 162

Why 162 on Cattell is not 162 on a Wechsler test

An IQ score means nothing without knowing its standard deviation - the number that sets how far apart the scores spread. Two people can be at the exact same percentile and get very different three-digit numbers depending on which test they took.

• The Wechsler tests (WAIS, WISC) use a standard deviation of 15. The 98th percentile lands at about 130.
• The Stanford-Binet historically used 16. The same 98th percentile lands at about 132.
• The Cattell III B, used by British Mensa, uses a standard deviation of 24. The same 98th percentile lands at 148.

Because the Cattell scale spreads scores more widely, its numbers run higher for the same rarity. That is why British Mensa admits people at 148 on Cattell but 130 on Wechsler - both are the "top 2%," just labelled differently. Lydia's 162 is roughly 2.6 standard deviations above the mean on that wide scale, which is why it functions as a ceiling: the paper simply does not produce a higher figure for a child. A 162 on a Wechsler test, by contrast, would be about 4 standard deviations out - a dramatically rarer event. Same digits, different meaning entirely.

None of this shrinks what Lydia did. Hitting the ceiling of a supervised, timed reasoning test at 12 is a real and rare achievement. It just means her 162 belongs to the Cattell ruler, and comparing it to a loose "160" attached to a physicist is comparing a measured mark on one scale to a guess with no scale at all.

The Einstein comparison is a headline, not a measurement

Every version of this story leaned on the same line: she beat Einstein and Hawking, who "scored 160." The problem is that neither number is real. British Mensa's own communications manager, Ann Clarkson, put it plainly at the time: the 160 attributed to Einstein and Hawking "is a bit of an urban myth - there is no evidence Einstein ever took a test, and if Hawking has, he has certainly never revealed the results."

So the comparison is a storytelling device, not a leaderboard. Einstein died in 1955; the modern group-administered IQ tests he is "ranked" against did not measure him. The "160" is a number later writers pinned to famous minds to give readers a familiar yardstick. Lydia herself was the clearest-eyed person in the whole affair. Told she had outscored the two physicists, she said she did not think she could be compared to "such great intellectuals," because "they've achieved so much" - a distinction between a test result and a life's work that most of the headlines missed.

That is the honest frame worth carrying away: a high childhood IQ score is a snapshot of reasoning ability on one afternoon, on one scale. It is a strong signal, not a prophecy, and it is not the same currency as a body of scientific work.

Where Lydia fits among "genius child" stories

Lydia was not even the only 12-year-old to hit 162 that year - a handful of British children have topped the Cattell scale in the same window, and the pattern repeats every few years because the test has a fixed ceiling that bright, well-prepared children can reach. These stories are real and they are also, in a sense, a feature of how the scale is built: a ceiling exists to be hit. If you want the fuller picture of measured versus mythical numbers, the famous-people hub below sorts the handful of genuine test scores from the many estimates.

Related

How to Join Mensa: The Test, Evidence Route and Steps

There are two ways to join Mensa: pass the supervised admission test, or submit proof of a top 2% score from an accepted test. Here is the full process, step by step.

Related

The Highest IQs in History: Estimated Scores of Great Minds

The highest IQs in history, like Goethe near 210 and Newton near 190, come from Catharine Cox's 1926 study, which estimated them from biographies, not tests.

FAQ

Q: What was Lydia Sebastian's IQ score?

A: 162, measured on a supervised British Mensa test in August 2015, when she was 12. It was scored on the Cattell III B scale, and 162 is the highest result the test gives to anyone under 18. It is a genuine, proctored score rather than an estimate.

Q: Did Lydia Sebastian really beat Einstein and Hawking?

A: Not in any measured sense. The "160" credited to Einstein and Hawking is, in British Mensa's own words, "a bit of an urban myth" - there is no evidence Einstein ever took an IQ test, and Hawking never released any result. Her 162 is real; their 160 is a number assigned to them later.

Q: Is a Cattell 162 the same as a 162 on a normal IQ test?

A: No. The Cattell III B uses a standard deviation of 24, while Wechsler tests use 15. Because the Cattell scale spreads scores more widely, its numbers run higher for the same rarity. A Cattell 162 is near that test's ceiling, not the once-in-a-nation event a 162 would be on a Wechsler scale.

Q: How high do you need to score to join Mensa?

A: The 98th percentile - the top 2%. On the Cattell III B that is 148; on a Wechsler test it is about 130. The threshold is the same rarity everywhere; only the scale's label changes.

References

• CNN - "British 12-year-old smarter than Einstein, Hawking" (Sept 2015)
• ScienceAlert - "12-Year-Old Girl Scores 162 in The Mensa IQ Test"
• British Mensa - How to qualify and the tests used

Last updated: July 13, 2026