Imagine taking out a 12-inch ruler and finding that the number 12 is on the left side and the number 1 is on the right side. For most native English speakers, this would be disorienting. We are used to seeing the numbers move from smallest to largest, from left to right. When this layout flips, people struggle because the numbers are now in the “wrong” place.

Psychologists have long known that people in Western cultures tend to associate smaller numbers with the left side of space and larger numbers with the right, a phenomenon called the SNARC effect – short for Spatial-Numerical Association of Response Codes.

In the lab, researchers like us test this tendency by asking people to press a left or a right button when shown a numerical digit. Native English speakers are generally quicker to press left for small numbers and right for large numbers because these locations match our mental number line.

But here’s the twist: What feels like the “correct” direction depends on where you grew up and where you live. In places with right-to-left languages like Arabic, the pattern often flips: People are faster to press right for small numbers and left for large numbers. Speakers of Farsi, a right-to-left language, who were born in Iran but move to France gradually shift toward a left-to-right mapping the longer they stay.

Even literacy matters. On average, people who never learned to read or count don’t show the........

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