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Murat Aydin, Michael Herzog, Haluk Ogmen; Compression in slit viewing occurs not in space but at object level. Journal of Vision 2007;7(9):213. doi: 10.1167/7.9.213.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose. When a figure moves behind a stationary narrow slit, observers often report seeing the figure as an integrated whole although only the part of the figure confined to the narrow area of the slit is visible at any single instant (anorthoscopic perception). We used this paradigm to investigate the principles of “non-retinotopic” form perception in human vision. In slit viewing, the figure is also perceived as compressed along the axis of motion. However, it is still unclear whether the space in the vicinity of the slit or the figure itself undergoes compression. In a psychophysical experiment, we tested these two hypotheses. In addition, we investigated the role of perceptual grouping in slit viewing.
Methods. The perceived width of a bar (width: 17 arcmin; height: 4 arcmin), flashed for 31 ms in the center of the slit area (21 arcmin wide), was measured both in isolation and in the presence of a moving circle (8.5 deg/s) behind the slit. The perceived width of the same bar was also measured while it was moving (8.5 deg/s) behind the slit, again both in isolation and in the presence of a circle moving in either the same or opposite direction.
Results. 1) In all conditions, the moving circle was perceived as compressed. 2) The perceived width of the flashed bar was similar regardless of whether the perceptually compressed moving circle was presented. 3) The perceived width of the moving bar was smaller when it was presented concurrently with the perceptually compressed circle moving in the same but not in the opposite direction.
Conclusion. Our results indicate that in non-retinotopic form perception, compression of form results from figural rather than spatial compression and that compression properties can transfer between objects if they are perceptually grouped (e.g. based on the Gestalt principle of “common fate”).
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