Colour as a Gestalt: Pop out with basic features and with conjunctions

Abstract

Gestalt phenomena are a cornerstone of perceptual psychology. Although sometimes poorly understood, they are powerful and robust effects with significant implications for how we recognize objects and parse scenes. Traditionally, the study of Gestalts has focused on visual form perception, where parts combine in nonadditive ways to create wholes possessing novel emergent properties different from the “sum of their parts”. Here I argue that colour perception meets the customary criteria applied to Gestalts at least well as shape perception does, in that colour emerges from nonadditive combination of wavelengths in the perceptual system and results in novel, emergent features. Regarding colour as a (and perhaps as the quintessential) Gestalt may help demystify Gestalts and help us better understand the role of colour in tasks such as visual search that are used to identify basic features in early vision. Colour should be thought of not as a basic feature or primitive property of the stimulus but rather as a complex conjunction of wavelengths that are integrated in perceptual processing. As a Gestalt, however, colour serves as a psychological primitive and so, as with Gestalts in form perception, it may lead to pop-out in visual search. Indeed, pop-out should be regarded as a prerequisite for claiming that a conjunction of features forms a Gestalt.