Bridging the Gap Between Object-Based Attention and Texton-Based Segmentation: How Attention Spreads Through Orientation-Defined Textures

Many recent studies of object-based attention (OBA) have suggested that the underlying units of attention are often discrete objects, through which attention readily spreads. However, the relationship of such experiments to the basic visual features (‘textons’) which guide the segmentation of visual scenes into ‘objects’ remains largely unexplored. Here we bridge this gap for one of the most conspicuous features of early vision: orientation. We do so in a study of how attention spreads through simple static orientation-defined textures (ODTs), and across texture-defined boundaries. Much work in the segmentation literature suggests that orientation-based texture segmentation (OBTS) is guided by orientation gradients, and our previous work suggests that it is also influenced by ODT curvatures. We suggest here that attention should respect ODT boundaries defined by both orientation and curvature differences, and we also predict that the flow of attention should not depend on the general direction (i.e. the ‘grain’) of the texture — in contradiction to previous findings in the OBA literature. We explore such predictions using both spatial-cueing and dividedattention paradigms on various ODTs, both uniform (one ‘object’) and discontinuous (two ‘objects’). Contrary to previous studies, we find that the texture’s ‘main direction’ has no effect: attention flows just as readily with vs. against the ‘grain’ of ODTs. At the same time, texture-defined discontinuities have a major effect: attention flows less readily across texture boundaries which are defined by either orientation or curvature. These effects replicated across multiple paradigms and dependent measures, and also held for jittered ODTs, wherein the effects must be due to global structure as opposed to local good continuation. We conclude that uniform ODTs are single objects from an attentional point of view, while discontinuous ODTs — with the discontinuities defined in either orientation or curvature — are processed as multiple objects. Collectively these experiments begin to reveal how the ‘objects’ of OBA are formed from simpler visual features.