The interplay of holistic shape, local feature and color information in object categorization

• We examine how color removal affects classification of intact and scrambled images.
• Performance and P1, N1, P2 and N2 event-related potentials (ERPs) are analyzed.
• Color removal interfered with classification of moderately scrambled stimuli only.
• For recognizable but scrambled images, color-related ERP modulations emerged.
• Colors are more important in cases when holistic processing is not efficient.

Although it is widely accepted that colors facilitate object and scene recognition under various circumstances, several studies found no effects of color removal in tasks requiring categorization of briefly presented animals in natural scenes. In this study, three experiments were performed to test the assumption that the discrepancy between empirical data is related to variations of the available meaningful global information such as object shapes and contextual cues. Sixty-one individuals categorized chromatic and achromatic versions of intact and scrambled images containing either cars or birds. While color removal did not affect the classification of intact stimuli, the recognition of moderately scrambled achromatic images was more difficult. This effect was accompanied by amplitude modulations of occipital event-related potentials emerging from approximately 150 ms post-stimulus. Our results indicate that colors facilitate stimulus classification, but this effect becomes prominent only in cases when holistic processing is not sufficient for stimulus recognition.