Abstract
Introduction We use luminance-defined (first-order) and texture-defined (second-order) boundaries to segregate abutting visual patterns. The discriminability of these boundaries varies with the visual system's spatial resolution, which decreases towards the periphery. Covert exogenous spatial attention inflexibly increases spatial resolution for first- and second-order textures, resulting in improved performance at peripheral locations but impaired performance at central retinal locations. In contrast, endogenous attention flexibly adjusts resolution to improve the discriminability of first-order textures at all locations; however, it is unknown if this also occurs with second-order textures. Here, we investigated whether endogenous and exogenous attention also differentially affect second-order textures. Methods Observers performed a 2IFC texture segmentation task. We used texture stimuli composed of a first-order carrier whose luminance contrast was modulated by a Gabor (target), ensuring that the target was discriminated from the background solely by a texture-defined boundary. The target was located at 7 possible eccentricities (0°–7.2°) on the horizontal meridian. In separate sessions, we manipulated either exogenous attention with brief peripheral cues or endogenous attention with central symbolic cues that informed observers of the upcoming target location, and compared performance with a neutral condition in which an uninformative cue was presented. Results Performance (d') in the neutral condition varied non-monotonically with eccentricity, peaking in the parafovea and declining towards the fovea and periphery. Exogenous and endogenous attention yielded distinct behavioral effects. When exogenous attention was manipulated, performance was impaired in the fovea, improved in the periphery, and the performance peak shifted farther into the periphery. In contrast, endogenous attention improved performance at all eccentricities without shifting the location of the peak. Conclusion Endogenous and exogenous attention differentially modulate second-order textures. Our results provide further evidence that exogenous attention inflexibly increases spatial resolution whereas endogenous attention flexibly adjusts resolution to facilitate behavior.
Meeting abstract presented at VSS 2018