The motion of the occluding surface enhances perceptual transparency R Actis-Grosso |
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Department of Psychology, University of Milano-Bicocca, Italy
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| When a stripe is partially overlapping a figure of different colour, it is possible to see the stripe as apparently transparent (i.e. the Rosenbach effect). This effect, which has also been dubbed phantom effect [e.g. Tynan and Sekuler, 1975, Science, 188, 951-952], is stronger when the occluded surface is moving. An experiment is presented, aimed at testing the role of motion of the occluding surface on the perception of transparency in the Rosenbach effect. Participants (n=12) were asked to judge, on a seven points Likert scale, the perceptual transparency of the occluding surface, which could be (a) static, (b) moving at a slow velocity (i.e. 3.7 cm/s) or (c) moving at a high velocity (i.e. 12.4 cm/s). Physical transparency, lightness-contrast and –polarity were also manipulated. Results show that the perception of transparency is enhanced when the occluding surface is moving: scores for perceptual transparency are higher for animations than for static images, and for slow animations as compared with fast animations (p<0.05). A significant interaction between Contrast and Transparency (p<0.0001) indicates that a low contrast facilitates the perception of transparency in physically opaque surfaces. A possible explanation is suggested, based on the role of both motion and simultaneous lightness contrast. |
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