In the 1860s, the German philologist Lazarus Geiger proposed that the subdivision of color always follows the same hierarchy. The simplest color lexicons (such as the DugermDani language of New Guinea) distinguish only black/dark and white/light. The next color to be given a separate word by cultures is always centered on the red part of the visible spectrum. Then, according to Geiger, societies will adopt a word corresponding to yellow, then green, then blue. Lazarus's color hierarchy was forgotten until restated in almost the same form in 1969 by Brent Berlin, an anthropologist, and Paul Kay, a linguist, when it was hailed as a major discovery in modern linguistics. It showed a universal regularity underlying the apparently arbitrary way language is used to describe the world.

Berlin and Kay's hypothesis has since fallen in and out of favor, and certainly there are exceptions to the scheme they proposed. But the fundamental color hierarchy, at least in the early stages (black/white, red, yellow/green, blue) remains generally accepted. The problem is that no one could explain why this ordering of color exists. Why, for example, does the blue of sky and sea, or the green of foliage, not occur as a word before the far less common red?

There are several schools of thought about how colors get named. "Nativists," who include Berlin and Kay argue that the way in which we attach words to concepts is innately determined by how we perceive the world. In this view our perceptual apparatus has evolved to ensure that we make "sensible"-that is, useful-choices of what to label with distinct words: we are hardwired for practical forms of language. "Empiricists," in contrast, argue that we don`t need this innate programming, just the capacity to learn the conventional (but arbitrary) labels for things we can perceive.

In both cases, the categories of things to name are deemed "obvious": language just labels them. But the conclusions of Loreto and colleagues fit with a third possibility: the "culturist" view, which says that shared communication is needed to help organize category formation, so that categories and language co-evolve in an interaction between biological predisposition and culture. In other words, the starting point for color terms is not some inevitably distinct block of the spectrum, but neither do we just divide up the spectrum in some arbitrary fashion, because the human eye has different sensitivity to different parts of the spectrum. Given this, we have to arrive at some consensus, not just on which label to use, but on what is being labeled.