Spelling and Intelligence: Are Bad Spellers Smart?

Spelling and intelligence are moderately related, mostly through verbal ability. In a study of 1,116 US children and teenagers, spelling skill correlated .56 with the vocabulary test from a standard IQ battery, while in a study of German third-graders the number of spelling mistakes correlated only -.17 with nonverbal IQ, so poor spelling on its own says little about how intelligent someone is.

Being a bad speller is also not a sign of high intelligence. Spelling is a learned skill that depends on stored knowledge of individual words, practice and reading experience. This page covers how strongly spelling tracks IQ, why spelling behaves like its own skill, what dyslexia research shows about spelling and IQ, and where the idea that bad spellers are secretly smart comes from.

The best recent data come from Rebecca Treiman and colleagues at the Colorado Learning Disabilities Research Center. They studied 1,116 children aged 8 to 17, one twin from each pair, and measured spelling and word reading with two tests each so they could model each skill as a "latent trait," a statistical estimate that strips out much of the measurement error in any single test. Spelling correlated .56 with the vocabulary subtest of the Wechsler Intelligence Scale for Children (WISC) and .58 with the WISC arithmetic subtest. Reading correlated .64 with vocabulary.

A correlation of .56 is substantial. Squaring it gives the share of differences the two measures have in common, about 30%. Children with larger vocabularies tend to spell better, but there is plenty of room for a child with a strong vocabulary to spell poorly and the reverse. The Colorado sample deliberately included many children with a history of reading difficulties or ADHD, which widens the range of scores and can make correlations somewhat larger than in an ordinary classroom.

The link with nonverbal reasoning is weaker. Katrin Hille and colleagues tested 194 third-grade boys in Germany on a culture-fair nonverbal intelligence test and a standard spelling test. The correlation between spelling mistakes and nonverbal IQ was -.17: higher-IQ boys made somewhat fewer mistakes, but nonverbal IQ accounted for only about 3% of the differences in spelling.

Put together, spelling sits with the verbal and literacy side of ability. It shares a good deal with vocabulary and reading, and much less with abstract reasoning.

Spelling and word reading are almost the same ability. In the Colorado study, the latent-trait correlation between them was .96. The authors note that English is harder to spell than to read, because the mapping from sounds to letters is less predictable than the mapping from letters to sounds. Spelling a word correctly often requires remembering that particular word's spelling, which takes exposure and practice rather than reasoning power.

Studies of adults who read well but spell poorly point the same way. Virginia Holmes and Anne Castles studied university students who were "unexpectedly poor spellers." Compared with good spellers, their misspellings showed less word-specific knowledge, though they knew the basic sound-to-letter rules just as well, and they were slower and less accurate at quickly analysing letter strings. Their disadvantage was not explained by reading less. These were capable students whose stored knowledge of exact spellings was thinner.

At the top end, spelling rewards effort. Angela Duckworth and colleagues followed competitors in the US National Spelling Bee over time and found that "deliberate practice," defined as studying and memorizing words alone, predicted performance better than being quizzed by others or reading for pleasure. The personality trait of "grit," meaning perseverance and passion for long-term goals, predicted final performance through the amount of deliberate practice. Elite spelling is built through hours of solitary study.

Genetic studies add one more piece. In a genome-wide analysis of up to 33,959 people aged 5 to 26, Else Eising and colleagues found a shared genetic factor that explained most of the variation in word reading, nonword reading, spelling and phoneme awareness, and it only partially overlapped with genetic variation for intelligence and educational attainment. Spelling draws on a literacy-specific set of influences as well as general ability.

Persistent difficulty with spelling is one of the core features of dyslexia, and dyslexia occurs across the IQ range. Under US federal rules, schools identified reading disabilities partly through an "IQ-discrepancy," a gap between a child's IQ and their reading or spelling scores. Linda Siegel argued in 1989 that IQ is irrelevant to defining a learning disability, presenting evidence that poor readers at a variety of IQ levels show similar reading, spelling, language and memory deficits.

A meta-analysis of 46 studies by Karla Stuebing, Jack Fletcher and colleagues supported much of that view. Poor readers whose reading lagged behind their IQ and poor readers whose reading matched their IQ overlapped heavily. Differences were negligible for behaviour (effect size -.05) and achievement (-.12), and small for cognitive ability (.30), with the cognitive differences largely explained by how the groups had been selected. In other words, a child's IQ tells you little about the nature of their reading problem. Our page on whether dyslexia affects IQ tests covers how examiners handle this during testing, and handwriting, a related writing skill, has its own page on IQ and handwriting.

If a child's spelling is far behind their reading level or their classmates, or an adult has long struggled with spelling and reading, the right person to see is an educational psychologist or another qualified assessor of specific learning difficulties.

The claim that poor spelling signals high intelligence has no direct research behind it. Its appeal is easy to see. Many people know someone sharp who cannot spell, and accomplished people who struggled with spelling make memorable stories. Memorable exceptions are not evidence of a pattern, and the correlations above run the other way: on average, better spellers have somewhat higher verbal ability.

Part of the claim is a reaction against the opposite habit of judging intelligence from spelling. In an experiment by Julie Boland and Robin Queen, 83 US adults rated email replies to a housemate advert. Replies containing typos or grammar errors such as "your" for "you're" drew more negative ratings of the writer on a 10-item scale that included how intelligent the writer seemed. People clearly judge writers by their errors, yet with a correlation of about .5 between spelling and verbal ability, that cue is weak for any single person. A misspelled email is a poor basis for judging someone's IQ in either direction.

No. Studies show a modest positive link between spelling and verbal ability, so on average better spellers score somewhat higher, and no study shows that poor spelling signals high intelligence.

Only weakly. Spelling correlated about .56 with an IQ-test vocabulary measure in a large study of children, and much less with nonverbal reasoning, so it reflects learned word knowledge more than general reasoning.

Yes. Spelling depends on stored knowledge of specific words, and capable university students and people with dyslexia can spell poorly despite strong reasoning skills.

The Wechsler intelligence scales, for example, include an oral vocabulary subtest but no spelling subtest. Spelling is measured by separate achievement tests.

Dyslexia is a difficulty with reading and spelling that occurs at all levels of IQ. Research comparing poor readers with higher and lower IQ scores found their reading and spelling problems looked very similar.

Spelling and intelligence are related, mainly through verbal ability, with correlations around .5 to .6 for vocabulary and much weaker links to nonverbal reasoning. Spelling is a learned skill built from reading and practice, it is nearly identical to word reading, and it can lag behind intelligence for many reasons, including dyslexia. Neither bad spelling nor good spelling is a reliable sign of someone's IQ. If you want a measure of reasoning ability that does not depend on spelling, you can take a full-length online IQ test.

1. Treiman, R., Hulslander, J., Willcutt, E. G., Pennington, B. F., & Olson, R. K. (2025). On the relationship between word reading ability and spelling ability. Reading and Writing, 38(6), 1509-1531. [doi.org/10.1007/s11145-024-10566-z](. doi.org

2. Hille, K., Gust, K., Bitz, U., & Kammer, T. (2011). Associations between music education, intelligence, and spelling ability in elementary school. Advances in Cognitive Psychology, 7, 1-6. [doi.org/10.2478/v10053-008-0082-4](. doi.org

3. Holmes, V. M., & Castles, A. E. (2001). Unexpectedly poor spelling in university students. Scientific Studies of Reading, 5(4), 319-350. [doi.org/10.1207/S1532799XSSR0504_02](. doi.org

4. Duckworth, A. L., Kirby, T. A., Tsukayama, E., Berstein, H., & Ericsson, K. A. (2011). Deliberate practice spells success: Why grittier competitors triumph at the National Spelling Bee. Social Psychological and Personality Science, 2(2), 174-181. [doi.org/10.1177/1948550610385872](. doi.org

5. Eising, E., Mirza-Schreiber, N., de Zeeuw, E. L., Wang, C. A., Truong, D. T., Allegrini, A. G., et al. (2022). Genome-wide analyses of individual differences in quantitatively assessed reading- and language-related skills in up to 34,000 people. Proceedings of the National Academy of Sciences, 119(35), e2202764119. [doi.org/10.1073/pnas.2202764119](. doi.org

6. Siegel, L. S. (1989). IQ is irrelevant to the definition of learning disabilities. Journal of Learning Disabilities, 22(8), 469-478. [doi.org/10.1177/002221948902200803](. doi.org

7. Stuebing, K. K., Fletcher, J. M., LeDoux, J. M., Lyon, G. R., Shaywitz, S. E., & Shaywitz, B. A. (2002). Validity of IQ-discrepancy classifications of reading disabilities: A meta-analysis. American Educational Research Journal, 39(2), 469-518. [doi.org/10.3102/00028312039002469](. doi.org

8. Boland, J. E., & Queen, R. (2016). If you're house is still available, send me an email: Personality influences reactions to written errors in email messages. PLOS ONE, 11(3), e0149885. [doi.org/10.1371/journal.pone.0149885](. doi.org

Hero image: Scrabble board 2007, by David Martyn Hunt, CC BY 2.0. Via Wikimedia Commons.