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On the left is shown a figure with perfect symmetry in terms of the colors as well as the positions of the elements: the symmetry is perceived effortlessly. Figure 1 provides a simple demonstration that we are sensitive to color in symmetry perception. That is, the human visual system is sensitive to the colors and not just the positions of features in the perception of symmetry. It is therefore not surprising that symmetry - an important biological feature - can be detected in isoluminant stimuli, that is stimuli defined solely by chromatic contrast 12. It is well-established that color (chromatic) contrast facilitates the detection of otherwise camouflaged objects 10, 11. In this communication we provide new psychophysical evidence concerning the role of color and attention-to-color in symmetry processing. Thus, understanding symmetry perception is at the very heart of understanding perceptual organization 9. symmetrical regions often tend to be seen as figure rather than ground), amodal completion 5 and visual search 6, and involves a widespread network of higher-tier extrastriate visual areas, such as V3A, V7, and LOC 7, 8. Psychophysical and brain imaging studies (fMRI) have shown that symmetry perception plays an important role in object recognition 1, 2, figure-ground segregation 3, 4 (e.g. Symmetry is a ubiquitous feature in natural images, and is found in both biological and man-made objects. Mirror-symmetry (from now on just ‘symmetry’) occurs when two halves of a pattern mirror each other.
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We conclude that mirror-symmetry detection mechanisms, while sensitive to color-correlations across the symmetry axis and subject to the benefits of attention-to-color, are not color selective. We found: (a) near-chance levels for the anti-symmetric condition, suggesting that symmetry perception is sensitive to color-correlations across the symmetry axis (b) similar performance for random-segregated and non-segregated conditions, giving no support to the idea that mirror-symmetry is color selective (c) highest performance for the color-segregated condition, but only when the observer knew beforehand the symmetry color, suggesting that symmetry detection benefits from color-based attention.
Nature knows no color line pdf trial#
We used four arrangements: (1) ‘segregated’ – symmetric blobs were of one color, random blobs of the other color(s) (2) ‘random-segregated’ – as above but with the symmetric color randomly selected on each trial (3) ‘non-segregated’ – symmetric blobs were of all colors in equal proportions, as were the random blobs (4) ‘anti-symmetric’ – symmetric blobs were of opposite-color across the symmetry axis. Stimuli consisted of colored Gaussian-blobs arranged either mirror-symmetrically or quasi-randomly. Some reports support the existence of color-selective mirror-symmetry channels, others that mirror-symmetry perception is merely sensitive to color-correlations across the symmetry axis. The role of color in the visual perception of mirror-symmetry is controversial.