Does colour impact responses to images in geckos?

Animals are exposed to different visual stimuli that influence how they
perceive and interact with their environment. Visual information such as
shape and colour can help the animal detect, discriminate and make
appropriate behavioural decisions for mate selection, communication,
camouflage, and foraging. In all major vertebrate groups, it has been
shown that certain species can discriminate and prefer certain colours and
that colours may increase the response to a stimulus. However, since
colour is often studied together with other potentially confounding
factors, it is still unclear what role colour plays in the perception of
and attention to biologically relevant and familiar stimuli versus novel
stimuli. In this study, we test whether colour influences the response
that an animal has to an object, and if this influence – if any – changes
depending on the object shown to the animal. We therefore assessed the
response of three gecko species Correlophus ciliatus, Eublepharis
macularius, and Phelsuma laticauda to familiar and novel objects presented
as colour or grayscale images. Our results indicate that colour did not
change the animal’s response to any of the objects. Specifically, we found
that while all species responded more often to the novel than to the
familiar images, colour did not influence the response. We also found that
the duration of interaction with images was significantly longer for the
diurnal species, P. laticauda, than for the two nocturnal species, but
this was again independent from colouration. Finally, no differences among
sexes were observed within or across species. Our results indicate that
geckos discriminate between 2D images of different content independent of
colouration, suggesting that colouration may not increase detectability or
intensity of the response. These results are essential for uncovering
which visual stimuli produce a response in animals