Mantis shrimp see the world with 4x more colour receptors than you

Human eyes have four types of photoreceptor. Mantis shrimp have between 12 and 16, tuned across ultraviolet, visible and polarised light — an eye that looks, on paper, like the best colour vision in the animal kingdom. Oddly, they seem to process it more crudely than expected, recognising broad categories fast rather than discriminating finely — nobody fully understands why evolution built such an elaborate sensor for such simple processing.

— Hanne Thoen et al., A Different Form of Color Vision in Mantis Shrimp — Science, 2014