Why Some Languages Count Colours Differently

[A] English speakers treat blue and green as separate colours and find the distinction obvious. Many languages do not make it. Welsh historically used a single term, glas, across a range that English would divide, and a number of languages across Africa and Asia do something similar. [B] The temptation is to conclude that speakers of those languages see differently, and for a time some researchers said exactly that.

[C] Careful testing has shown something more interesting. Speakers of a language with one term for blue and green can distinguish the shades perfectly well when asked to sort them; what changes is speed, not capacity. Shown two patches and asked whether they match, a speaker whose language divides them answers a fraction faster, because the label does part of the work. [D] The effect is real and it is small. There is also a pattern to which distinctions appear. Languages with only two colour terms divide light from dark; a third term is almost always red; green and yellow follow, and blue arrives later still. The order is remarkably consistent across unrelated families, which suggests that the naming of colour is shaped by something other than culture alone.