What is more important when searching for an object in a real-world scene: foveal vision or extrafoveal vision? This question was assessed in an object search experiment where gaze-contingent display changes created artificial Blindspots and Spotlights. In a 2(+1) x 3 design, the type of image degradation (Blindspots / Spotlights (+Control)) was crossed with three window sizes (radii: 1.6, 2.9, and 4.1 deg). Gaze-centered Blindspots and Spotlights were created on the fly by blending the original colored scene photograph and a low- pass filtered version of it into each other via a spatial Gaussian weight mask. When searching the scene with artificially impaired central vision (Blindspots), search performance was relatively unimpaired, highlighting the importance of extrafoveal scene analysis in search. Artificially impairing extrafoveal scene analysis (Spotlights) affected attentional selection and visual processing; smaller windows led to a reduced likelihood of finding the target, longer search times, and shorter saccades. The 4.1 deg window was identified as the cross-over point of equal search times in Blindspot and Spotlight conditions. However, a gaze-data based decomposition of RTs into search initiation time, scanning time, and verification time [Malcolm & Henderson, 2009, Journal of Vision, 9(11), 13] revealed differences in particular sub-processes of search.
|Conference||16th European Conference on Eye Movements|
|Period||21/08/11 → 25/08/11|