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Combining S-cone and luminance signals adversely affects discrimination of objects within backgrounds.

Jennings, Ben J.; Tsattalios, Konstantinos; Chakravarthi, Ramakrishna; Martinovic, Jasna


Ben J. Jennings

Konstantinos Tsattalios

Ramakrishna Chakravarthi

Jasna Martinovic


The visual system processes objects embedded in complex scenes that vary in both luminance and colour. In such scenes, colour contributes to the segmentation of objects from backgrounds, but does it also affect perceptual organisation of object contours which are already defined by luminance signals, or are these processes unaffected by colour's presence? We investigated if luminance and chromatic signals comparably sustain processing of objects embedded in backgrounds, by varying contrast along the luminance dimension and along the two cone-opponent colour directions. In the first experiment thresholds for object/non-object discrimination of Gaborised shapes were obtained in the presence and absence of background clutter. Contrast of the component Gabors was modulated along single colour/luminance dimensions or co-modulated along multiple dimensions simultaneously. Background clutter elevated discrimination thresholds only for combined S-(L+M) and L+M signals. The second experiment replicated and extended this finding by demonstrating that the effect was dependent on the presence of relatively high S-(L+M) contrast. These results indicate that S-(L+M) signals impair spatial vision when combined with luminance. Since S-(L+M) signals are characterised by relatively large receptive fields, this is likely to be due to an increase in the size of the integration field over which contour-defining information is summed.


JENNINGS, B.J., TSATTALIOS, K., CHAKRAVARTHI, R. and MARTINOVIC, J. 2016. Combining S-cone and luminance signals adversely affects discrimination of objects within backgrounds. Scientific reports [online], 6, article number 20504. Available from:

Journal Article Type Article
Acceptance Date Jan 5, 2016
Online Publication Date Feb 9, 2016
Publication Date Dec 31, 2016
Deposit Date Mar 14, 2016
Publicly Available Date Mar 14, 2016
Journal Scientific reports
Electronic ISSN 2045-2322
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 6
Article Number 20504
Keywords Colour vision; Human behaviour
Public URL


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