This Optical Illusion Makes You Question Which Bus Is Moving Faster
Which of the buses in this “race” is moving more quickly? Neither, as it seems, as both of them are actually traveling at the same speed. This may seem unlikely at first, but quickly becomes apparent when the background changes to a solid gray.
Dubbed the Stepping Feet Illusion, the motion perception phenomenon first shows a blue and yellow bus moving horizontally across a “street”—with alternating black and white stripes.
While, in truth, both buses are moving side by side, the beholder perceives them to be driving at different speeds, with each seemingly moving more quickly at different instances due to the contrast against the background.
Image via Stepping Feet Illusion GIF: Rinuraeni / Wikipedia (CC BY-SA 4.0)
According to Wikipedia, when the blue bus reaches a white stripe, the higher contrast of the two colors makes it more easily visible to our eye, thus making it appear to move faster than its actual speed.
Inversely, when it passes a black stripe, the low contrast between the dark colors makes it more difficult to perceive, so its movement looks slower. The opposite effects ring true for the bus in yellow.
“Overall, the higher-contrast movements look faster than those with lower contrast. The effect disappears when the street’s striped texture is removed because there is no contrast remaining,” reads the explanation.
This illusion, named because the buses resembled feet walking, was first demonstrated by UC San Diego psychologist Stuart Anstis in 2003. He used it to explain in a paper why cars seemed to be “slowing down in foggy conditions.”
[via Boing Boing and Wikipedia, images via Stepping Feet Illusion GIF: Rinuraeni (CC BY-SA 4.0)]
