Object-based attentional selection in scene viewing: Evidence from fixation position effects

29 January 2013
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Two contrasting views of visual attention in scenes are the visual salience and the cognitive relevance hypotheses. They fundamentally differ in their conceptualization of the visuospatial representation over which attention is directed. According to the saliency model, this representation is image-based, while the cognitive relevance framework advocates an object-based representation. To test these hypotheses, we investigated where people fixate within real objects and saliency proto-objects. We found a preferred viewing location (PVL) close to the center of objects within naturalistic scenes. Factors that modulate the PVL include object size, the direction of the incoming saccade, and the distance between the object and the previous fixation (i.e., launch site distance). Moreover, we examined how within-object fixation position affected subsequent eye-movement behavior on the object. Unexpectedly, there was no refixation Optimal Viewing Position (OVP) effect for objects in scenes. A fixation-duration Inverted-Optimal Viewing (IOVP) effect was found for large objects only. Compared to the PVL for real objects, there was less evidence for a PVL for human fixations within saliency proto-objects. There was no evidence for a PVL when only saliency proto-objects that did not spatially overlap with annotated real objects were analyzed. Collectively, the results suggest that objects are important units of saccadic selection in scene viewing. Visual saliency mainly acts through its correlation with objects.