Object-based attention (OBA) enhances processing within the boundaries of a selected object. Larger OBA effects have been observed for horizontal compared to vertical rectangles, which were eliminated when controlling for attention shifts across the visual field meridians. We aimed to elucidate the modulatory role of the meridians on OBA. We hypothesized that the contralateral organization of visual cortex accounts for these differences in OBA prioritization. Participants viewed BL^-shaped objects and, following a peripheral cue at the object vertex, detected the presence of a target at the cued location (valid), or at a non-cued location (invalid) offset either horizontally or vertically. In Experiment 1, the single displayed object contained components crossing both meridians. In Experiment 2, one cued object and one non-cued object were displayed such that both crossed the meridians. In Experiment 3, one cued object was sequestered into one screen quadrant, with its vertex either near or far from fixation. Results from Experiments 1 and 2 revealed a horizontal shift advantage (faster RTs for horizontal shifts across the vertical meridian compared to vertical shifts across the horizontal meridian), regardless of whether shifts take place within a cued object (Experiment 1) or between objects (Experiment 2). Results from Experiment 3 revealed no difference between horizontal and vertical shifts for objects that were positioned far from fixation, although the horizontal shift advantage reappeared for objects near fixation. These findings suggest a critical modulatory role of visual field meridians in the efficiency of reorienting object-based attention.

Object-based attention (OBA) enhances processing within an attended object. We previously found that attention shifts that crossed the visual field meridians were faster horizontally than vertically, which we named a Shift Direction Anisotropy (SDA). We aimed to determine whether the SDA depends upon attention shift meridian crossings of object boundaries, target locations, or both. Participants viewed an ‘L’-shaped object and responded to a target at the cued vertex location (valid) or at non-cued object locations offset horizontally (invalid-horizontal) or vertically (invalid-vertical). In Experiment 1, object boundaries and target locations were positioned either crossing or not crossing the meridians. In Experiments 2A and 2B, object boundaries were held constant (always crossing or never crossing the meridians, respectively) while target locations were manipulated (randomly crossing or non-crossing). In Experiments 3A and 3B, target locations were held constant while object boundaries were manipulated. In Experiment 4, the object was removed to determine whether object-based or space-based attentional resources were being deployed. The SDA emerged only when target locations necessitated shifts that crossed the meridians, regardless of object placement, demonstrating that the SDA is driven by target location relative to the meridians and that OBA processes prioritize specific target locations within an object.

Object-based attention (OBA) enhances processing within an attended object. We previously found that attention shifts that crossed the visual field meridians were faster horizontally than vertically, which we named a Shift Direction Anisotropy (SDA). We aimed to determine whether the SDA depends upon attention shift meridian crossings of object boundaries, target locations, or both. Participants viewed an 'L'-shaped object and responded to a target at the cued vertex location (valid) or at non-cued object locations offset horizontally (invalid-horizontal) or vertically (invalid-vertical). In Experiment 1, object boundaries and target locations were positioned either crossing or not crossing the meridians. In Experiments 2A and 2B, object boundaries were held constant (always crossing or never crossing the meridians, respectively) while target locations were manipulated (randomly crossing or non-crossing). In Experiments 3A and 3B, target locations were held constant while object boundaries were manipulated. In Experiment 4, the object was removed to determine whether object-based or space-based attentional resources were being deployed. The SDA emerged only when target locations necessitated shifts that crossed the meridians, regardless of object placement, demonstrating that the SDA is driven by target location relative to the meridians and that OBA processes prioritize specific target locations within an object.

No abstract