Brief article Categorical perception of colour in the left and right visual field is verbally mediated: Evidence from Korean q Debi Roberson * , Hyensou Pak, J. Richard Hanley Department of Psychology, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom Received 30 April 2007; revised 30 August 2007; accepted 1 September 2007 Abstract In this study we demonstrate that Korean (but not English) speakers show Categorical perception (CP) on a visual search task for a boundary between two Korean colour categories that is not marked in English. These effects were observed regardless of whether target items were presented to the left or right visual field. Because this boundary is unique to Korean, these results are not consistent with a suggestion made by Drivonikou [Drivonikou, G. V., Kay, P., Regier, T., Ivry, R. B., Gilbert, A. L., Franklin, A. et al. (2007) Further evidence that Whorfian effects are stronger in the right visual field than in the left. Proceedings of the National Academy of Sciences 104, 1097–1102] that CP effects in the left visual field provide evidence for the existence of a set of universal colour categories. Dividing Korean participants into fast and slow respond- ers demonstrated that fast responders show CP only in the right visual field while slow respond- ers show CP in both visual fields. We argue that this finding is consistent with the view that CP in both visual fields is verbally mediated by the left hemisphere language system. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Colour categories; Colour; Cultural relativity; Visual search; Categorical perception 0010-0277/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cognition.2007.09.001 q This research is supported by Economic and Social Research Council Grant RES/221527 to the first author and by a Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF-2006-352-H00003) to Dr. Hyensou Pak. * Corresponding author. Tel.: +44 01206 874175/3710; fax: +44 01206 873590. E-mail address: robedd@essex.ac.uk (D. Roberson). www.elsevier.com/locate/COGNIT Available online at www.sciencedirect.com Cognition 107 (2008) 752–762