How do we see colour?

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The evolution, neuroscience and psychology of colour perception

Colour has been a part of life for at least 1.1 billion years, when we know early organisms were coloured with light red pigments. Colour is now an important product of the human mind and the environment, precisely because our minds, and those of other animals, are so tuned in to it. As a primate, we are member of the most colourful group of mammals. In primates colour is used to identify members of one’s own species, as well as to determine information about age, sex, mating quality, mating status, and emotional state – such as when a person’s face turns red with rage, or one’s cheeks blush red with embarrassment.

Humans belong to the catarrhines, the most visual group among primates, most of which routinely have high visual acuity, binocular vision, and three independent channels for conveying colour information, known as trichromacy. Trichromacy has its basis in the diversity of our opsin photopigments, which are coded for by a gene family that has expanded in our lineage, alongside a decrease in the gene family for smell. Interestingly, as colour vision became more important, and the sense of smell less so, such primates relied more on trichromacy for the foraging of fruit and foliage, with the specialized identification each of these proposed to, in turn, have driven its appearance, such as the redness of ripe fruit. Of course, some people have forms of colour blindness that arise from not having the opsins available to trichromats, limiting the range of colours that can be seen.

Colours themselves have individual significance. Some colour preferences occur across distantly related species, with animals as distant as insects being like humans in to preferring to look at blue over red. In humans and other primates red is associated with social dominance. However humans show subtle differences from each other in their perception of colours, let alone their preferences of them. While some of these differences have been related to particular aspects of culture, such as colour vocabulary, others factors seem to be more complex remain more elusive, such as why people view illusions such as #thedress differently.

This and many other colour illusions reveal how colour is not simply a quality of objects out there in the world, but also something constructed and computed in the human brain based on prior experience and the context that a colour appears within. Thus, when experiencing the Colourscape experience at the Holburne, or looking at the colourful artwork within the Museum, consider how what surrounds a colour might impact your experience of it, and how millions and billions of years have led to that moment of experience.

Dr Alexandra de Sousa
College of Liberal Arts, Bath Spa University
Crossmodal Cognition Lab, Department of Psychology, University of Bath

Dr Michael Proulx
Crossmodal Cognition Lab, Department of Psychology, University of Bath