Abstract
Stimuli briefly flashed just before a saccade are perceived closer to the saccade target, a phenomenon known as perisaccadic compression of space (Ross et al., 1997). More recently, we have demonstrated that brief probes are attracted towards a visual reference when followed by a mask, even in the absence of saccades (Zimmermann et al., 2014a). Here, we ask whether spatial compression depends on the transient disruptions of the visual input stream caused by either a mask or a saccade. Both of these degrade the probe visibility but we show that low probe visibility alone causes compression in the absence of any disruption. In a first experiment, we varied the regions of the screen covered by a transient mask, including areas where no stimulus was presented and a condition without masking. In all conditions, we adjusted probe contrast to make the probe equally hard to detect. Compression effects were found in all conditions. To obtain compression without a mask, the probe had to be presented at much lower contrasts than with masking. Comparing mislocalizations at different probe detection rates across masking, saccades and low contrast conditions without mask or saccade, Experiment 2 confirmed this observation and showed a strong influence of probe contrast on compression. Finally, in Experiment 3, we found that compression decreased as probe duration increased both for masks and saccades although here we did find some evidence that factors other than simply visibility as we measured it contribute to compression. Our experiments suggest that compression reflects how the visual system localizes weak targets in the context of highly visible stimuli.
Highlights
Understanding how we perceive and construct the visual space around us is a fundamental task in vision science with a long tradition in philosophy, psychology, neuroscience and other disciplines
There was no evidence that a transient disruption of the visual input stream by the mask was critical for compression to occur
Error Trials and Probe Visibility Trials immediately discarded and repeated due to violations of the fixation or saccade instructions amounted to 3.5% in the control, 3.7% in the mask, 7.1% in the saccade, and 2.0% in the ‘‘none’’ condition
Summary
Understanding how we perceive and construct the visual space around us is a fundamental task in vision science with a long tradition in philosophy, psychology, neuroscience and other disciplines (see Khurana and Nijhawan, 2010; Melcher, 2011). Despite the explicit location information provided by these spatial maps, objects are sometimes seen at positions other than their true locations. The perceived locations of probes around the time of saccadic eye movements have long been studied for the insight they give us about how spatial coordinates are updated when the retinal image shifts. The saccade target seems to attract the flashed probe, a phenomenon known as saccadic compression of space This is one of the best-known and most-cited effects in the eye movement literature and numerous computational models have been developed to explain it (e.g., Morrone et al, 1997; VanRullen, 2004; Hamker et al, 2008; Richard et al, 2009; Pola, 2011; Cicchini et al, 2013). The transformation from preto post-saccadic coordinates guided by extraretinal oculomotor signals (e.g., eye position or efference copy signals) that interact with the visual input
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