The science of intelligence
Verbal vs nonverbal intelligence
Short answer
Verbal intelligence is reasoning with words plus the vocabulary and knowledge you have built up; research models call much of it comprehension-knowledge (Gc). Nonverbal intelligence is reasoning with shapes, patterns and designs. The two are correlated parts of general ability, and they age differently: vocabulary keeps rising into the sixties, while some nonverbal reasoning peaks in the twenties.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
What counts as verbal and nonverbal
Verbal intelligence covers reasoning that runs through language: knowing what words mean, understanding a passage, explaining how two ideas are alike, answering general knowledge questions. Nonverbal intelligence covers reasoning with shapes, patterns, sequences and designs, where the problem is shown rather than described.
The split overlaps with an older one. Raymond Cattell distinguished fluid intelligence, reasoning with novel material, from crystallized intelligence, acquired knowledge, in 1963 (Wikipedia: Fluid and crystallized intelligence). Most verbal tasks lean on crystallized knowledge, and most nonverbal puzzles are designed to tap fluid reasoning, though the match is not perfect. The fluid vs crystallized guide covers that distinction on its own.
Where they sit in models of intelligence
In the Cattell-Horn-Carroll framework, much of verbal ability falls under comprehension-knowledge (Gc), while nonverbal puzzles draw on fluid reasoning (Gf) and visual processing (Gv). A 2023 network analysis of the Woodcock-Johnson IV norm sample supported these as separate broad abilities (McGrew et al., 2023). Working memory splits the same way: the Baddeley and Hitch model has a phonological loop for verbal information and a visuospatial sketchpad for visual and spatial material (Hitch et al., 2025).
Separate does not mean unrelated. The 1994 mainstream statement held that while there are different types of intelligence tests, some using words or numbers and others shapes or designs, they all measure the same intelligence (Gottfredson, 1997). Plomin and Deary report that different cognitive abilities correlate about 0.30 on average at the observed level, but about 0.60 or higher genetically (Plomin & Deary, 2015). Uneven profiles are common, and so is a shared core.
Try one · Quantitative Reasoning
Which number comes next?
3, 8, 15, 24, 35, 48, ?
Tap the option you think is right, or show the answer.
Show the answer
The next number is 63 (option 5).
How to solve it
- The gaps (5, 7, 9, 11, 13) grow by 2 each time, which is the pattern of square numbers.
- Each number is a square number minus 1: 2 × 2 - 1, 3 × 3 - 1, 4 × 4 - 1, 5 × 5 - 1, 6 × 6 - 1, 7 × 7 - 1.
- So the next number is 8 × 8 - 1 = 63.
That was 1 puzzle. The full test has 25.
Some tests report both
Several clinical batteries report a verbal score and a nonverbal or performance score alongside the full-scale IQ. The split can reveal things a single number hides. In the PROBIT breastfeeding trial, which followed 13,889 children to age 6.5 using the Wechsler Abbreviated Scale of Intelligence, the breastfeeding-promotion group scored 7.5 points higher on verbal IQ (95% confidence interval +0.8 to +14.3) but only 2.9 points higher on performance IQ, with an interval from -3.3 to +9.1 that includes zero (Kramer et al., 2008). The verbal difference was the clearer one.
They change differently with age
Verbal knowledge and nonverbal reasoning follow different paths across adulthood. Processing speed and some reasoning measures peak in the late teens and twenties, while vocabulary and accumulated knowledge keep rising into the sixties (Hartshorne & Germine, 2015). Across generations the pattern also differs: a 2015 meta-analysis of the Flynn effect found annual gains of 0.41 IQ points for fluid test performance but 0.21 for crystallized performance (Pietschnig & Voracek, 2015).
Reading feeds more than vocabulary
You might expect reading to boost only verbal skills. A study of 1,890 identical-twin pairs tested from ages 7 to 16 found that the twin who read better earlier tended to show higher intelligence later, and the associations were not restricted to verbal abilities (Ritchie, Bates & Plomin, 2015). Because identical twins share their genes, the comparison removes genetic differences as an explanation. More on outside influences is in how environment shapes intelligence.
Why nonverbal tests exist
Verbal items depend on the language and schooling a person has had. The 1994 statement noted that people who do not understand English well can be given a nonverbal test or one in their native language (Gottfredson, 1997). That is the main appeal of nonverbal formats such as matrices, and it is why they are popular for online tests. They reduce the role of language; they do not remove culture entirely. See what a nonverbal IQ test is and culture-fair IQ tests.
The IQ Octopus test is entirely nonverbal: 25 visual puzzles across pattern recognition, abstract, spatial, quantitative and logical reasoning, scored as an estimated IQ. For a short warm-up in the same style, try the nonverbal reasoning test, and for the visual side in more depth, read spatial intelligence.
Sources
- Fluid and crystallized intelligence. Wikipedia. en.wikipedia.org/wiki/Fluid_and_crystallized_intelligence
- McGrew, K. S., Schneider, W. J., Decker, S. L., & Bulut, O. (2023). A psychometric network analysis of CHC intelligence measures. Journal of Intelligence, 11(1), 19. doi.org/10.3390/jintelligence11010019
- Gottfredson, L. S. (1997). Mainstream science on intelligence: An editorial with 52 signatories, history, and bibliography. Intelligence, 24(1), 13-23. doi.org/10.1016/S0160-2896(97)90011-8
- Hitch, G. J., Allen, R. J., & Baddeley, A. D. (2025). The multicomponent model of working memory fifty years on. Quarterly Journal of Experimental Psychology, 78(2), 222-239. doi.org/10.1177/17470218241290909
- Hartshorne, J. K., & Germine, L. T. (2015). Psychological Science, 26(4), 433-443. doi.org/10.1177/0956797614567339
- Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains. Perspectives on Psychological Science, 10(3), 282-306. doi.org/10.1177/1745691615577701
- Plomin, R., & Deary, I. J. (2015). Molecular Psychiatry, 20, 98-108. doi.org/10.1038/mp.2014.105
- Kramer, M. S., et al. (2008). Breastfeeding and child cognitive development: New evidence from a large randomized trial. Archives of General Psychiatry, 65(5), 578-584. doi.org/10.1001/archpsyc.65.5.578
- Ritchie, S. J., Bates, T. C., & Plomin, R. (2015). Does learning to read improve intelligence? Child Development, 86(1), 23-36. doi.org/10.1111/cdev.12272