The uses of colour vision: behavioural and physiological distinctiveness of colour stimuli

Abstract

Colour and greyscale (black and white) pictures look different to us, but it is not clear whether the difference in appearance is a consequence of the way our visual system uses colour signals or a by-product of our experience. In principle, colour images are qualitatively different from greyscale images because they make it possible to use different processing strategies. Colour signals provide important cues for segmenting the image into areas that represent different objects and for linking together areas that represent the same object. If this property of colour signals is exploited in visual processing we would expect colour stimuli to look different, as a class, from greyscale stimuli. We would also expect that adding colour signals to greyscale signals should change the way that those signals are processed. We have investigated these questions in behavioural and in physiological experiments.We find that male marmosets (all of which are dichromats) rapidly learn to distinguish between colour and greyscale copies of the same images. The discrimination transfers to new image pairs, to new colours and to image pairs in which the colour and greyscale images are spatially different.We find that, in a proportion of neurons recorded in the marmoset visual cortex, colour-shifts in opposite directions produce similar enhancements of the response to a luminance stimulus.We conclude that colour is, both behaviourally and physiologically, a distinctive property of images.

The marmoset monkey as a model for visual neuroscience

“…Most of what is known about marmoset visual behavior derives from either natural ethological observations or neuropsychological experiments carried out in a small number of laboratories (Ridley et al, 1986; Roberts et al, 1990; Derrington et al, 2002; Burkart and Heschl, 2006; Schiel and Huber; 2006; Hook and Rogers, 2008; Kemp and Kaplan, 2013). Recent work has shown that it is also possible to carry out controlled experiments in head-fixed, awake marmosets, where oculomotor behavior and visual stimulation can be precisely determined (Mitchell et al, 2014; Hung et al, 2015).…”

Possible functions of contextual modulations and receptive field nonlinearities: Pop-out and texture segmentation

“…This is illustrated in Figure 3A: the elephant and the tree have similar color and luminance, but the texture difference of its skin compared to the tree provides a sufficient cue for the object boundary. In addition, detecting texture boundaries and color boundaries along with luminance boundaries is helpful for distinguishing shadows from object boundaries (Derrington et al, 2002; Johnson & Baker, 2004; Johnson, Kingdom, & Baker, 2005; Kingdom, 2003; Kingdom, Beauce, & Hunter, 2004; Schofield, Rock, Sun, Jiang, & Georgeson, 2010). This is because texture borders are often aligned with luminance borders in natural scenes (Johnson & Baker, 2004; Johnson et al, 2005), but shadows lying across an otherwise uniform surface are associated with luminance changes but no other cues such as color or texture changes.…”

Comparative study of the photopic spectral sensitivity of domestic ducks (Anas platyrhynchos domesticus), turkeys (Meleagris gallopavo gallopavo) and humans

“…However, the functional significance of colour vision in some areas of the spectrum has yet to be determined (Honkvaara et al, 2002). For others, such as UV A perception, several explanations have been suggested (Cuthill et al, 2000;Derrington et al, 2002). UV A perception enhances the ability of some birds to find seeds, berries and insects that reflect UV A radiation (Burkhardt, 1982;Siitari et al, 1999;Siitari and Hovi, 2002).…”