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The question of whether language affects our categorization of perceptual continua is of particular interest for the domain of color where constraints on categorization have been proposed both within the visual system and in the visual environment. Recent research Roberson et al., in press) found substantial evidence of cognitive color differences between different language communities, but concerns remained as to how representative might be a tiny, extremely remote community. The present study replicates and extends previous findings using additional paradigms among a larger community in a different visual environment. Adult semi-nomadic tribesmen in Southern Africa carried out similarity judgments, short-term memory and long-term learning tasks. They showed different cognitive organization of color to both English and another language with the five color terms. Moreover, Categorical Perception effects were found to differ even between languages with broadly similar color categories. The results provide further evidence of the tight relationship between language and cognition.

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The Whorf hypothesis holds that differences between languages induce differences in perception and/or cognition in their speakers. Much of the experimental work pursuing this idea has focused on the domain of color and has centered on the issue of whether linguistically coded color categories influence color discrimination. A new perspective has been cast on the debate by recent results that suggest that language influences color discrimination strongly in the right visual field but not in the left visual field (LVF). This asymmetry is likely related to the contralateral projection of visual fields to cerebral hemispheres and the specialization of the left hemisphere for language. The current study presents three independent experiments that replicate and extend these earlier results by using different tasks and testing across different color category boundaries. Our results differ in one respect: although we find that Whorfian effects on color are stronger for stimuli in the right visual field than in the LVF, we find that there are significant category effects in the LVF as well. The origin of the significant category effect in the LVF is considered, and two factors that might account for the pattern of results are proposed.color categories ͉ hemispheric lateralization ͉ linguistic relativity ͉ visual search T he Whorf hypothesis holds that semantic differences between languages induce differences in perception and/or cognition in their speakers (1). Much of the experimental work pursuing this idea has focused on the domain of color and has centered on the issue of whether linguistically coded color categories influence color discrimination (2-13). A new perspective has been cast on the debate by recent results of Gilbert et al. (14), which suggest that language influences color discrimination strongly in the right visual field (RVF) and less so or not at all in the left visual field (LVF). This asymmetry likely is related to the contralateral projection of visual fields to cerebral hemispheres and the specialization of the left hemisphere (LH) for language. It suggests that, within an individual, the Whorf hypothesis may be relevant for processing within one hemisphere and not the other. In consequence, under normal conditions, perceivers may view the world at once filtered through the lens of their language and not so filtered.In the Gilbert et al. study (14), subjects were given a visual search task that required detection of a single target color among 11 identical distractors. The target differed from the distractors in hue, and it was either of a different named category from the distractors (e.g., a blue among greens) or it was from the same category as the distractors (one blue among examples of another blue). The target-distractor perceptual differences for betweencategory (also known as across-category) discriminations were no greater on average than for within-category discriminations, yet between-category discriminations were significantly faster, but only when the target occurred in the RVF. Beca...

Both adults and infants are faster at discriminating between two colors from different categories than two colors from the same category, even when between-and within-category chromatic separation sizes are equated. For adults, this categorical perception (CP) is lateralized; the category effect is stronger for the right visual field (RVF)-left hemisphere (LH) than the left visual field (LVF)-right hemisphere (RH). Converging evidence suggests that the LH bias in color CP in adults is caused by the influence of lexical color codes in the LH. The current study investigates whether prelinguistic color CP is also lateralized to the LH by testing 4-to 6-month-old infants. A colored target was shown on a differently colored background, and time to initiate an eye movement to the target was measured. Target background pairs were either from the same or different categories, but with equal target-background chromatic separations. Infants were faster at initiating an eye movement to targets on different-category than same-category backgrounds, but only for targets in the LVF-RH. In contrast, adults showed a greater category effect when targets were presented to the RVF-LH. These results suggest that whereas color CP is stronger in the LH than RH in adults, prelinguistic CP in infants is lateralized to the RH. The findings suggest 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.language and thought ͉ nature/nurture ͉ lateralization ͉ perceptual development C ategorical perception (CP) of color is shown when two colors that belong to different color categories (between-category judgments) are discriminated faster, or more accurately, than two colors belonging to the same color category (within-category judgments), even when between-and within-category chromatic separation sizes are equated (1). ʈ This effect is found in adults (2-5), children and toddlers (6, 7), and infants (8-10). The role of language in the effect has been extensively debated (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). For example, some have advanced the hypothesis that the on-line use of language is the origin of the effect: comparing stimulus labels aids discrimination for between-category pairs and/or hinders discrimination for within-category pairs. In support of this hypothesis, for adult participants, CP is found only if the category boundary is marked in the participant's language (3, 12, 13), and verbal interference eliminates CP, but visual interference does not (4,5,13,14). It has, however, been found that color CP occurs prelinguistically in toddlers and infants, who have no color language (6,(8)(9)(10).A recent set of studies looking at hemispheric asymmetries in color CP has added a new perspective on the debate. Gilbert et al. (14), using a visual search task, found that the time to detect a colored target among differently colored distractors was faster when target and distractors were from different categories (e.g., bl...

Color perception can be categorical: Between-category discriminations are more accurate than equivalent within-category discriminations. The effects could be inherited, learned, or both. The authors provide evidence that supports the possibility of learned categorical perception (CP). Experiment 1 demonstrated that observers' color discrimination is flexible and improves through repeated practice. Experiment 2 demonstrated that category learning simulates effects of "natural" color categories on color discrimination. Experiment 3 investigated the time course of acquired CP. Experiment 4 found that CP effects are acquired through hue-and lightness-based category learning and obtained interesting data on the dimensional perception of color. The data are consistent with the possibility that language may shape color perception and suggest a plausible mechanism for the linguistic relativity hypothesis.This article explores the nature and origin of color categorization by considering how categorical perception (CP; e.g., Harnad, 1987), linguistic relativity (e.g., Whorf, 1940Whorf, /1956, and perceptual learning (e.g., Goldstone, 1998) are related. These three areas of inquiry overlap because, first, differences in CP across languages are one manifestation of linguistic relativity (e.g., Kay & Kempton, 1984), and, second, perceptual learning is a likely route through which language influences color cognition, and more specifically through which CP is induced. Our experiments explored whether adult color discrimination can be improved through training and whether CP is induced by learning novel color categories. We argue that if they can be, then this increases the plausibility that similar mechanisms may be involved during language learning, giving rise to relativistic effects. Before explicating this sketch of our argument further, we briefly review each of the three areas.

Roberson and Davidoff (2000) found that color categorical perception (CP; better cross-category than within-category discrimination) was eliminated by verbal, but not by visual, interference presented during the interstimulus interval (ISI) of a discrimination task. On the basis of this finding, Roberson and Davidoff concluded that CP was mediated by verbal labels, and not by perceptual mechanisms, as is generally assumed. Experiment 1 replicated their results. However, it was found that if the interference type was uncertain on each trial (Experiment 2), CP then survived verbal interference. Moreover, it was found that the target color name could be retained across the ISI even with verbal interference (Experiment 3). We therefore conclude that color CP may indeed involve verbal labeling but that verbal interference does not necessarily prevent it.

Performance of a wide range of simple visual tasks improves with practice. Here we ask whether such learning occurs for the fundamental visual task of luminance contrast detection. In two experiments we find that contrast sensitivity increases following extensive practice at detecting briefly presented sinusoidal luminance gratings and that learning is maintained after six months. Learning is spatial frequency tuned, specific to retinal location and can be specific to one eye, but is not selective for orientation. The selectivity of learning implies that it is based on plasticity in early visual, as opposed to central cognitive, processing mechanisms.