An experiment found that the brain uses one set of neural circuits to identify the numbers 1–4; these circuits are very specific to their own numbers. A separate set of circuits respond to the numbers 5–9; these are less precise, and are activated by adjacent numbers.
For this reason, it is easier to determine when there are four things than to determine there are five things.
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This has been part of IQ tests for a while: the vast majority of people can hold to 4 items without a problem, some people struggle with that, some people can hold to 5, 6, 7 or rarely more objects without a problem.
It’s also why phone numbers in most places started as 5 digit numbers, then as “area code + 7”, and now that we use smartphone contact lists to save them, they’ve gone to full “country code + 9 + extension”. There was also an interesting movement opposing the changes: https://www.mentalfloss.com/article/61116/why-did-old-phone-numbers-start-letters
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I don’t think that’s why, not least because this is a recent discovery. The reason is, presumably, because 26+ keys are difficult to fit on a small but still usable keyboard.
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Yes. And they had letters grouped with the numbers because 26+ keys is a lot to fit on a small but still usable keyboard (or dial, originally).
This is cool. I always wondered why I can instantly grasp 1 through 4, but 5 and up become abstract. Thank you for posting this!
