No abstract

Stimulus displacements coinciding with a saccadic eye movement are poorly detected by human observers. In recent years, converging evidence has shown that this phenomenon does not result from poor transsaccadic retention of presaccadic stimulus position information, but from the visual system's efforts to spatially align presaccadic and postsaccadic perception on the basis of visual landmarks. It is known that this process can be disrupted, and transsaccadic displacement detection performance can be improved, by briefly blanking the stimulus display during and immediately after the saccade. In the present study, we investigated whether this improvement could also follow from a discontinuity in the task-irrelevant form of the displaced stimulus. We observed this to be the case: Subjects more accurately identified the direction of intrasaccadic displacements when the displaced stimulus simultaneously changed form, compared to conditions without a form change. However, larger improvements were still observed under blanking conditions. In a second experiment, we show that facilitation induced by form changes and blanks can combine. We conclude that a strong assumption of visual stability underlies the suppression of transsaccadic change detection performance, the rejection of which generalizes from stimulus form to stimulus position.

Multiple times per second, the visual system succeeds in making a seamless transition between presaccadic and postsaccadic perception. The nature of the transsaccadic representation needed to support this was commonly thought to be sparse and abstract. However, recent studies have suggested that detailed visual information is transferred across saccades as well. Here, we seek to confirm that preview effects of visual detail on postsaccadic perception do indeed occur. We presented subjects with highly similar artificial shapes, preceded by a congruent, an incongruent, or no preview. Postsaccadic recognition performance was measured, while the contrast of presaccadic and postsaccadic stimuli was manipulated independently. The results show that congruent previews provided a benefit to the recognition performance of postsaccadic stimuli, compared to no-preview conditions. Incongruent previews induced a recognition accuracy cost, combined with a recognition speed benefit. A second experiment showed that these effects can disappear when stimulus presentation is interrupted with a postsaccadic visual mask. We conclude that visual detail contained in transsaccadic memory can affect the postsaccadic percept. Furthermore, we find that the transsaccadic representation supporting this process is contrast-independent, but that postsaccadic contrast, through its effect on the reliability of information, can affect the degree to which it is employed.

To study perceptual grouping processes, vision scientists often use stimuli consisting of spatially separated local elements that, together, elicit the percept of a global structure. We developed a set of methods for constructing such displays and implemented them in an open-source MATLAB toolbox, GERT (Grouping Elements Rendering Toolbox). The main purpose of GERT is to embed a contour in a field of randomly positioned elements, while avoiding the introduction of a local density cue. However, GERT's modular implementation enables the user to create a far greater variety of perceptual grouping displays, using these same methods. A generic rendering engine grants access to a variety of element-drawing functions, including Gabors, Gaussians, letters, and polygons.