A simple animation has been found to offer our brains many possible interpretations. Jan Kremláček from Charles University in Hradec Králové, Czech Republic, discovered six different ways of perceiving a moving sine graph drawn with dots. The curves often seem to undulate like two ribbons, but the animation can also seem to have depth, with one curve seeming to be further back than the other. The dotted arcs can also look like a spindle shape that revolves and snakes along.
If you keep staring, the curves can seem to revolve vertically around a static rod, first in one direction, then the other. The animation can also look like a series of bouncing dots, but this is very hard to perceive without overlaying vertical bars on top of it. "Our brain is able to reconstruct different learned interpretations, but only one can be perceived at a time," says Kremláček. He came across the illusion by chance while preparing graphs for a lecture in signal processing.
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