From: The World In Your Head by Steven Lehar
Fig. 4.12 The properties of wave propagation demonstrate an emergent diffuse style of spatial interaction suggestive of emergence in perception. (A) Raindrops striking a pond create an incoherent pattern of radiating rings, that generally cancel by destructive interference. (B) If a line of raindrops strike the pond simultaneously, their expanding rings would collectively define an advancing wavefront propagating at right angles to the line of drops. (C) If the raindrops arrive along a line at equal intervals in space and time, their collective action defines a wavefront propagating along the line of drops. (D) Lines of raindrops arrriving coherently along an oblique front generate an emergent wavefront along that oblique front. These properties suggest a unique holistic principle of computation in perception.