Abstract
The relationship between language and colour categorisation is explored testing the predictions of the linguistic relativity hypothesis. The basic colour terms of Turkish are investigated, with findings suggesting that the Berlin and Kay (1969) theory of universal colour term evolution might require further revisions. The maximum number allowed by the theory is exceeded by the Turkish colour term inventory, by an extra term in the blue region. This difference between Turkish and English is exploited to test the effects of linguistic categories on colour perception and cognition. Evidence is presented suggesting that some aspects of categorical colour perception may not be fixed and universal, but flexible and culture-specific. Perceived similarity of colours seems to be open to influence by a linguistic category boundary. The argument of flexibility is further investigated using a category learning paradigm. Evidence suggested that perceptual and cognitive effects of colour category boundaries might be acquired through laboratory training. Subjects judge colours to be different more accurately when they come from different categories acquired in training than when they are from the same category. Mechanisms, which may be responsible for such flexibility, are explored in relation to findings in the literature. It is argued that perception and cognition may not be distinguished from each other by clear-cut boundaries. Rather, and interaction between percepts and concepts may facilitate effects of language and learning on human colour categorisation.