Are perceptual categories really conceptual?
A series of cross-cultural investigations, which had set out to replicate the seminal work of Rosch Heider with the Dani of New Guinea, not only failed to find evidence of a set of universal colour categories, but instead found evidence of inguistic relativity in both the English speaking and the Papua New Guinean populations tested. Participants from a rational hunter-gatherer culture, whose language contains five basic colour terms showed no tendency towards a cognitive organisation of colour resembling that of English speakers, (Roberson, Davies & Davidoff, 2000). Recent evidence from both normal English speakers (Roberson & Davidoff, 2000) and an English speaking neuropsychological patient (Roberson, Davidoff & Braisby, 1999) had also suggested that verbal coding plays a crucial role in determining perceptual categories for colour and facial expression. It is concluded that any universal constraints on the possible range of perceptual categories (at least for colour and facial expression) are of a generalised cognitive nature (such as grouping by similarity) rather than of a physiological nature.