Running head: CATEGORICAL PERCEPTION OF COLOR Neurophysiological Evidence for Categorical Perception of Color

The aim of this investigation was to examine the time course and the relative contributions of perceptual and post-perceptual processes to categorical perception (CP) of color. A visual oddball task was used with standard and deviant stimuli from same (within-category) or different (between-category) categories, with chromatic separations for within-and between-category stimuli equated in Munsell Hue. CP was found on a behavioral version of the task, with faster RTs and greater accuracy for between-compared to within-category stimuli. On a neurophysiological version of the task, event-related potentials (ERPs) showed earlier latencies for P1 and N1 components at posterior locations to between-relative to within-category deviants, providing novel evidence for early perceptual processes on color CP. Enhanced P2 and P3 waves were also found for between-compared to within-category stimuli, indicating a role for later post-perceptual processes. 3 Although the color spectrum is continuous, we perceive it as a number of qualitatively discreet 'perceptual categories' that we label in English with terms such as red, green, yellow, blue. Categorical differences between colors also appear to affect color discrimination. For example, adults are faster and more accurate at discriminating between two colors that cross a category boundary (between-category), than two colors from within the same category, even when the difference in hue is equated for between-and within-category stimulus pairs (e. Despite the robustness and generality of the category effect shown in color CP, the nature of CP is a matter of debate. On the one hand, as the term implies, the category effect could be due to greater perceptual discriminability around category boundaries than discriminability within categories The argument over perceptual versus linguistic accounts of CP is unresolved because performance on many of the tasks used to investigate color CP could be influenced by perceptual processes, or by linguistic processes, or by both. To 4 determine whether linguistic or perceptual processes (or both) underpin color CP, manipulations that differentially affect linguistic and perceptual processes are required, such as blocking the use of language (e. Boroditsky, 2007), or using 'markers' that indicate the presence (or absence) of perceptual and linguistic processes. To this end, some neurophysiological markers of perception are found to be generally impervious to semantic and syntactic manipulations. These include early event-related potential (ERP) components, such as an ERP approach a powerful means of examining perceptual contributions to color CP. The current investigation therefore takes a new approach to investigating the nature of CP, using …