The internal evidence of language has always implied that our brains have separate ways of processing One, Two, Three, Four, Many. Languages have basic words or grammatical forms for 1 2 3 and sometimes 4. Beyond 4, the later developed numbers take over, but without any grammatical connections.
A new study firms up the brain structures for digits, and adds a few more numbers on the specific side of the equation.
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The recent study actually indicates, however, that we do indeed process small and large numbers of things differently. The research groups involved in the project were able to demonstrate some years ago that the brain has nerve cells responsible for each number. Some neurons fire, for example, primarily for two elements, other for four elements and again others for seven elements.
“However, the neurons also fire in response to slight variations in the number,” explains Prof. Andreas Nieder from the University of Tübingen, who was the other main author of the study alongside Mormann. “A brain cell for a number of “seven” elements thus also fires for six and eight elements but more weakly. The same cell is still activated but even less so for five or nine elements.”
When a brain cell for a number of three things fires, it simultaneously inhibits the brain cells for the numbers two and four. This reduces the risk that these cells will also incorrectly fire for the number three. However, this mechanism does not exist for the neurons activated for numbers five, six or eight. This is why there is a higher error rate for these numbers.
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Sharp detection of deltas is unsurprising. That’s the primary purpose of senses. Why would a delta in counting matter? Best guess is keeping track of eggs or babies in a nest. Birds know when one egg has been stolen, and dogs know when one puppy is missing. Dogs have 8 tits, which determines the max litter size and also fits neatly with the new set of digits. Birds aren’t limited by boob count, but Google indicates that 4-6 eggs is typical for most songbirds, with max around 12.
Humans have only 2 spigots, but for most of history polygamy and complex social structures enabled load-sharing. I find it interesting that the rise of monogamy parallels the loss of the higher grammatical numbers both spatially and temporally.
Sideways inhibition is a new finding, and nicely parallels the pixels of the eye and the frequency-selecting hair cells of the ear.
Polistra's Mill 