Kinetic depth effect
![The Spinning Dancer is a kinetic, bistable optical illusion resembling a pirouetting female dancer. Some observers initially see the figure as spinning clockwise and some anticlockwise. Additionally, some may see the figure suddenly spin in the opposite direction. The illusion derives from an inherent ambiguity from the lack of visual cues for depth. There are other optical illusions that originate from the same or similar kind of visual ambiguity, such as the Necker cube. If you focus on one part of her body, such as her foot and the shadow, it is possible to switch back and forth by focusing on the opposite motion that she is currently performing with her foot. When trying to switch from clockwise to counterclockwise wise I have found focusing on the shadow of her foot for a couple seconds allows you to see the opposite direction. And in some cases when able to switch back and forth with ease it looks like she is waving her leg back and forth and has lost the spinning effect entirely. .](/Images/godic/202501/22/Spinning_Dancer4512.gif")
In visual perception, the kinetic depth effect refers to the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving. In the absence of other visual depth cues, this might be the only perception mechanism available to infer the object's shape. Being able to identify a structure from a motion stimulus through the human visual system was shown by Wallach and O'Connell in the 1950s through their experiments.