While you sit at your computer monitor and look at this image, the face on the left looks like an angry old man, while the one on the right looks like a calm woman.
Step back from your computer five or ten feet, and you will see that the images seem to change places!
According to Philippe Schyn and Aude Oliva of the University of Glasgow, this optical illusion “illustrates the ability of the visual system to separate information coming from different spatial frequency channels. “Coarse features and fine features are distinguished differently at different distances.When both sets of features are blended into one image, the mind sees the different feature sets, depending on the distance of the viewer. Technically put, “Hybrid images change interpretation as a function of viewing distance.”