Quantitative studies of animal colour constancy: using the chicken as model

Abstract

Colour constancy is the capacity of visual systems to keep colour perception constant despite changes in the illumination spectrum. Colour constancy has been tested extensively in humans and has also been described in many animals. In humans, colour constancy is often studied quantitatively, but besides humans, this has only been done for the goldfish and the honeybee. In this study, we quantified colour constancy in the chicken by training the birds in a colour discrimination task and testing them in changed illumination spectra to find the largest illumination change in which they were able to remain colour-constant. We used the receptor noise limited model for animal colour vision to quantify the illumination changes, and found that colour constancy performance depended on the difference between the colours used in the discrimination task, the training procedure and the time the chickens were allowed to adapt to a new illumination before making a choice. We analysed literature data on goldfish and honeybee colour constancy with the same method and found that chickens can compensate for larger illumination changes than both. We suggest that future studies on colour constancy in non-human animals could use a similar approach to allow for comparison between species and populations.

Farbensehen der Tiere

“…Das schärft die Farbunterscheidung und verbessert die Farbkonstanz [42]. Vögel könnendaherim fürdenMenschensicht-baren Spektralbereich sehr feine Farbunterschiede sehen, wie Untersuchungen an Hühnern und Wachteln [43][44][45] vor Kurzem bestätigt haben. Gleichzeitig nehmendie ÖltröpfchenaberauchLicht weg, sodass die absolute Empfindlichkeit der Zapfen abnimmt (.…”

Relative colour cues improve colour constancy in birds

“…As stimuli, we used the same type of conical food containers with random patterns of 30% coloured tiles and 70% grey tiles as in previous studies (Olsson et al, 2015(Olsson et al, , 2016Osorio et al, 1999). The tiles differed in intensity, and the range of intensities was larger for the grey than for the colour tiles.…”

“…Colour differences between stimuli and between different illumination colours were calculated using the receptor noise limited (RNL) model of colour vision , and achromatic contrasts were described as Michelson contrast for the double cone (for details, see Olsson et al, 2015Olsson et al, , 2016. The RNL model assumes that colours are coded by opponent mechanisms and discrimination thresholds are set by receptor noise.…”

“…Without colour constancy, colour information would be unreliable (Chittka et al, 2014). Many other animals are also colour constant (Balkenius and Kelber, 2004;Chittka et al, 2014;Dörr and Neumeyer, 2000;Neumeyer, 1998;Olsson et al, 2016). In humans, relational colour constancy, recovery of the chromatic relationship between colours in a changed illumination, is faster and more reliable (Foster and Nascimento, 1994) than absolute colour constancy, the exact recovery of the perceived colour.…”

“…We built on earlier experiments on chicken colour constancy (Olsson et al, 2016), but this time trained them to use relative cues, rewarding them for choosing an orange colour over a yellow unrewarded colour, thus allowing them to solve the task by choosing the relatively 'redder' colour. We quantified colour constancy performance by determining the size of the shift in illumination over which chickens could still discriminate colours.…”