Stepping feet illusion

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2022-08-14 07:30:03

The stepping feet illusion is a motion perception phenomenon involving two "buses," one blue and one yellow, moving horizontally across a "street" consisting of black and white stripes. Although both of the buses move at a constant speed, their perceived speed varies dramatically.[1][2][3]

When the blue bus lies on the white stripes, the contrast is high (dark blue vs. white) and easily visible, so it appears to move faster than its actual speed.[1][2][3] On the contrary, when the blue bus is against the black stripes, the contrast is low (dark blue vs. black) and harder to see, so the movement looks slower (see figs. 1 and 2).[1][2][3] The opposite effects occur for the yellow bus.[4][5] The two buses resemble a pair of moving of feet, giving the illusion its name.[6]

Overall, the higher-contrast movements look faster than those with lower contrast.[1][4][5] The effect disappears when the street's striped texture is removed because there is no contrast remaining,[6] showing how an object's background can have a significant effect on its perceived speed.[7]