Data from: Interaction between stimulus contrast and pre-saccadic crowding

Objects that are briefly flashed around the time of saccades are mislocalized. Previously, robust interactions between saccadic perceptual distortions and stimulus contrast have been reported. It is also known that crowding depends on the contrast of the target and flankers. Here, we investigated how stimulus contrast and crowding interact with pre-saccadic perception. We asked observers to report the orientation of a tilted Gabor presented in the periphery, with or without four flanking vertically oriented Gabors. Observers performed the task either following a saccade or while maintaining fixation. Contrasts of the target and flankers were independently set to either high or low, with equal probability. In both the fixation and saccade conditions, the flanked conditions resulted in worse discrimination performance—the crowding effect. In the unflanked saccade trials, performance significantly decreased with target-to-saccade onset for low-contrast targets but not for high-contrast targets. In the presence of flankers, impending saccades reduced performance only for low-contrast, but not for high-contrast flankers. Interestingly, average performance in the fixation and saccade conditions was mostly similar in all contrast conditions. Moreover, the magnitude of crowding was influenced by saccades only when the target had high contrast and the flankers had low contrasts. Overall, our results are consistent with modulation of perisaccadic spatial localization by contrast and saccadic suppression, but at odds with a recent report of pre-saccadic release of crowding.

在眼跳（saccade）前后短暂呈现的物体易出现定位偏差。既往研究已报道，眼跳相关知觉畸变与刺激对比度之间存在显著的交互作用；同时，视觉拥挤（crowding）效应的强弱依赖于目标与侧翼刺激的对比度。本研究探讨了刺激对比度与视觉拥挤如何共同影响眼跳前（pre-saccadic）知觉。实验中，要求被试报告外周呈现的倾斜Gabor刺激（Gabor）的朝向，该刺激可伴随或不伴随四个垂直朝向的侧翼Gabor刺激；被试分别在完成眼跳任务或保持固视（fixation）的状态下执行实验。目标与侧翼刺激的对比度被独立设置为高或低，且两种设置的出现概率相等。无论是固视还是眼跳条件，带有侧翼刺激的试次判别表现均更差，即出现典型的视觉拥挤效应。在无侧翼刺激的眼跳试次中，低对比度目标的判别表现随目标呈现至眼跳起始的时间间隔变化而显著下降，而高对比度目标则无此变化。当存在侧翼刺激时，即将发生的眼跳仅在侧翼刺激为低对比度时会降低判别表现，高对比度侧翼刺激则不会产生此类影响。值得注意的是，在所有对比度条件下，固视与眼跳条件下的平均表现整体较为相似；此外，仅当目标为高对比度且侧翼刺激为低对比度时，眼跳才会对视觉拥挤效应的强度产生调控作用。总体而言，本研究结果支持对比度与眼跳抑制（saccadic suppression）对眼跳间期（perisaccadic）空间定位的调控机制，但与近期一项关于眼跳前视觉拥挤效应解除的研究报道存在分歧。