Wednesday, March 05, 2008

Categorical color perception: the language effect

I touched on the sapir-whorf hypothesis and how Russians are better able to do better Categorical Perception (CP) of color, thanks to the fact that they have a richer color terms lexicon than English, last month.

I have also covered the research of P. Kay earlier regarding color terms and their evolution. Now a new PNAS paper by Kay et al shows that while the left hemisphere(LH) , which is involved in language, shows superior CP effect in adults, the reverse trend is shown in infants i.e.e the infants show a stronger CP of colors when the stimuli is presented to Left Visual field (LVF) and hence processed by RH.

Their hypothesis was that while the CP of colors in adults is mediated by language, the CP in infants is non-verbal and the cP in adults may or may not build on this childhood CP ability. The results go on to show that not only doers language affect the left hemisphere dominance on categorical perception of colors ; it does so by overriding an inborn RH dominance for the same task. thus, there is no doubt that the color term lexicon heavily influences how we categorize colors in the adulthood.


Here is their conclusion:

Evidence suggesting that color CP varies cross-linguistically, and that color CP is eliminated by verbal interference, has supported the hypothesis that color CP depends on access to lexical codes for color . However, the finding of color category effects in prelinguistic infants and toddlers has led others to argue that language cannot be the only origin of the effect . The current study finds evidence to support both positions. Color CP is found in 4- to 6-month-old infants, replicating previous infant studies. However, the absence of a category effect in the LH for infants, but the presence of a greater LH than RH category effect for adults, suggests that language-driven CP in adults may not build on prelinguistic CP, but that language instead imposes its categories on a LH that is not categorically prepartitioned. The current findings may therefore suggest a compromise between the two positions: there is a form of CP that is nonlinguistic and RH based (found in infancy) and a form of CP that is lexically influenced and biased to the LH (found in adulthood). Color CP is found for both infants and adults, but the contribution of the LH and RH to color CP appears to change across the life span.

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