Abstract
In the natural world, some animals display highly specific patterns that are conserved across members of a species. One form of patterning is thought to enable some animals (often toxic or unpalatable) to be easily seen, and possibly easily remembered, so as to warn off potential predators. These patterns, often high contrast in both colour and luminance, are known as warning signal patterns. I will review what is known about such warning signals in nature, and how they are studied. I will then describe research that uses modelling of the first stages of visual processing, combined with behavioural experiments using real predators, to demonstrate how warning signals might have specific effects on the brain that other patterns do not.