to study different wavelength colour matching in three adult pure breed dogs. Associative learning was also used by Neitz et al. recently showed that colour proved to be more informative than brightness when dogs choose between visual stimuli differing both in brightness and hue. However, the most employed technique of testing colour vision in dogs uses associative learning with a food reward. Ĭolour vision tests in the animal kingdom include both spontaneous and learned behaviour. Īlthough early behavioural studies on dogs' colour vision produced conflicting results (reviewed by ), recent behavioural studies support the presence of dichromatic vision in canine species, indicating that colour cues are important for dogs during their normal activities under natural photonic lighting conditions. Furthermore, dogs can discriminate brightness differences but their ability is about two times worse than in humans. This is owing to the different neural structures of the dogs' eyes and in particular to the fewer connections of the rods to the ganglion cells and the smaller number of optic nerve fibres. Concerning visual acuity, dogs are less able than humans to perceive clearly all the details of an object (four to eight time worse than humans). The presence of these two discrete cone subtypes indicates a potential dichromatic vision.

Specifically, visual-evoked potential and immunohistochemical studies have demonstrated that dogs possess two classes of cone pigments, one sensitive to long/medium wavelength light (555 nm spectral sensitivity red/green) and the other sensitive to short wavelength light (429 nm spectral sensitivity blue). Dogs' retinal structure clearly provides the potential for colour vision.

Are dogs color blind