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Barbara A. Drescher, Miguel P. Eckstein; Prior expectations of context and saccadic decisions in natural scenes. Journal of Vision 2004;4(8):339. doi: https://doi.org/10.1167/4.8.339.
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Many studies have shown that the 1st saccade during search is guided by visual information about the target and systematically increases with target/distractor discriminability (Williams, 1988; Findlay, 1997; Eckstein et al., 2000). Recently it has been shown that 1st search saccade performance improves with prior knowledge about the probable target location (Ciamataro et al., 2001; Oliva et al., 2003). The present study investigates the role of scene context in visual search and observers' prior expectations of target locations employing stimuli comprised of natural scenes. We compare 1st saccade performance (accuracy) when an object appears in an expected location (e.g., a reading lamp on a nightstand) vs. an unexpected location (e.g., the same reading lamp in the middle of a bed). Methods: On each trial an image was presented and observers searched for an everyday object (e.g., reading lamp) within the scene. In one set of scenes, objects were placed in an “expected” location as determined by an independent panel. In another set of scenes the objects were located in an “unexpected” location. In a final set, the target object was not present. Eye position and latency of eye movements were recorded. Results: performance accuracy of the 1st saccade improved when the target object appeared at an expected location rather than an unexpected location. Conclusion: Observer prior expectations about where an object might appear in a scene influences saccadic performance.
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