The Dancing Diamonds Illusion

The illusion of movement reported relies on luminance changes and phasing of fills to produce an array of diamonds so dazzling that to the observer they seem to have a life of their own! Furthermore, an interesting figure-ground reversal can be seen in the illusion when adjusting diamond size. However, it is the complexity of movement seen that is of prime interest and which gives the illusion its name. There is an underlying rationale as to why the diamonds appear to dance (Shapiro, et al. 2005. JOV (5)764-82). However, the interactions in the illusion are intriguing and we examined a variety of factors that contribute to this and which may be used to optimise the illusory sense of motion. Amongst these we found that i) the background luminance; ii) luminance of the diamond edges, and iii) diamonds' size, and configuration play a significant role. The illusion also demonstrates some differences between foveal and peripheral vision where apparent motion is influenced by viewing distance. Furthermore, if viewers get close enough to the screen to position the retinal image of a single diamond exactly on their fovea. The diamond does not move whilst the others seen in peripheral vision, continue their dance.