Abstract
Previous research has reported dramatic localization errors around the time of an eye movement. Stimuli briefly flashed just before a saccade are perceived closer to the saccade target, a phenomenon known as perisaccadic compression of space (Ross, Morrone, & Burr, 1997). We have demonstrated that similar mislocalizations of flashed stimuli can be observed in the absence of saccades (Zimmermann, Fink, & Cavanagh, 2013): Brief probes were attracted towards a visual reference when followed by a mask. We extend these studies to examples with a pair of references that draw the probe into the gap between them. Strong compression was found when we presented the reference stimuli followed by the mask, whereas little or no compression occurred for the reference pair alone. When the two references were arranged vertically, horizontal mislocalizations prevailed. That is, probes presented to the left or right of the vertically arranged references were "drawn in" to be seen aligned with the references. In contrast, vertical localization of the probes remained almost unaffected by the mask. This finding may be related to reports of perisaccadic compression of space being stronger parallel than orthogonal to the saccade vector. In contrast, when we arranged the two references horizontally, we found vertical compression for stimuli presented above or below the references. But we also observed horizontal mislocalizations: Probes were more strongly attracted by the left reference. Finally, when participants were to indicate the perceived probe location by making an eye movement towards it, saccade landing points were compressed in a similar fashion as perceptual judgments, indicating that the oculomotor system followed the perceptual illusion. Our findings challenge pure oculomotor accounts of perisaccadic compression of space. We suggest that perisaccadic and perifixational compression of space both reflect how the visual system deals with disruptions and discuss the potential role of correspondence matching.
Meeting abstract presented at VSS 2014