Matched objects seen closer when masked E Zimmermann1, G Fink1, P Cavanagh2 |
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1Institute of Neuroscience and Medicine 3, Research Centre Juelich, Germany |
| In cases of brief gaps in visual input caused by saccade eye movements or masks the visual system must match corresponding objects from before and after the disruption. We first presented a salient visual reference and followed it with a probe date and a mask. The relative timing of the probe and mask was varied and subjects estimated the position of the probe in relation to a comparison bar that was presented later. The probe location was reported accurately when presented long before or after mask onset. However, when the probe was presented within 50 ms of the mask, the probe appeared shifted toward the reference by as much as 50 percent of their separation. This attraction effect had spatial and temporal characteristics that were similar to the compression effect seen when visual input is interrupted by a saccade rather than a mask (Ross et al, 1997). Further tests showed that the amount of attraction was greater when object features (orientation) of anchor and probe matched. We interpret the attraction / compression effect as the result of a mechanism that computes a likely offset between corresponding objects based on the motion energy that accompanies their displacement. |
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