Motion dazzle: a locust's eye view

Motion dazzle describes high-contrast patterns (e.g. zigzags on snakes and dazzle paint on World War I ships) that do not conceal an object, but inhibit an observer's perception of its motion. However, there is limited evidence for this phenomenon. Locusts have a pair of descending contralateral movement detector (DCMD) neurons which respond to predator-like looming objects and trigger escape responses. Within the network providing input to a DCMD, separate channels are excited when moving edges cause areas of the visual field to brighten or darken, respectively, and these stimuli interact antagonistically. When a looming square has an upper half and lower half that are both darker than background, it elicits a stronger DCMD response than the upper half does alone. However, when a looming square has a darker-than-background upper half and a brighter-than-background lower half, it elicits a weaker DCMD response than its upper half does alone. This effect allows high-contrast patterns to weaken and delay DCMD response parameters implicated in escape decisions, and is analogous to motion dazzle. However, the motion dazzle effect does not provide the best means of motion camouflage, because uniform bright squares, or low-contrast squares, elicit weaker DCMD responses than high-contrast, half dark, half bright squares.