How Chromaticity Guides Visual Search in Real-World Scenes

To study visual attention during search processes, numerous studies measured the selectivity of observers’ saccadic eye movements for local display features. These experiments almost entirely relied on simple, artificial displays with discrete search items and features. Recently, a first study on saccadic selectivity in real-world scenes was conducted, demonstrating visual guidance by low-level features such as intensity and spatial frequency (Pomplun, 2006). However, that study only used grayscale displays, because chromaticity is assumed to dominate search behavior in such a way that it might be difficult to measure concurrent guidance by other dimensions. To test this assumption and to assess the effects of chromaticity on visual search performance, time course, and feature guidance in real-world displays, the present study measured eye movements during two versions of a set of 160 real-world displays: One version contained its natural colors, whereas the other version was converted to grayscale. The results indicate that the hue dimension indeed dominates search at the cost of other dimensions, and that chromaticity information leads to faster target detection without influencing the high-level, strategic control of visual attention.