Sunlight and “Blue”: The Prevalence of Poor Lexical Color Discrimination Within the “Grue” Range

We respond here to two Commentaries regarding our article (Lindsey & Brown, 2002) on the relationship worldwide between color names and ultraviolet-B (UV-B) insolation. Before addressing the specific issues raised in those Commentaries, we review the central thesis we advanced in that report. In a study of the published literature on color naming in world languages, we reported that languages spoken in the tropics, where the annual dose of UV-B radiation from sunlight is high, tend to lack a distinct word for ‘‘blue.’’ Instead, they use a single basic color term (BCT) that means green-or-blue (called ‘‘grue’’ here and in the literature) or that means green-or-blue-or-black. We argued that this clearly cultural phenomenon depends at least in part on color appearance, which in turn is constrained by the physiology of the visual system. We suggested that this tendency to lack a distinct word for ‘‘blue’’ may be partly due to environmental damage to the eyesight of the speakers of the languages in question. We investigated whether this damage could be due to the phototoxic effects of the ultraviolet radiation from sunlight, which can damage the retina (acquired tritan defect) and cause the ocular lens to turn brown (brunescence). A laboratory-based ‘‘virtual reality’’ experiment showed that young English speakers, when viewing colorimetrically adjusted stimuli that quantitatively simulated the appearance of the stimulus and its immediately surrounding environment as if viewed through a deeply brunescent ocular lens, tended to use the words ‘‘green’’ or ‘‘gray’’ for colors they would normally call ‘‘blue’’ or ‘‘purple.’’ Thus, damage to the ocular lens, if it is severe enough, would be sufficient to explain the lack of ‘‘blue’’ in many tropical languages. We did not examine in detail other phototoxic effects on the eye, or other possible environmental insults to vision that might also correlate with latitude, so it is not possible to apportion the putative causes of ocular damage among these alternatives.