The above image (which was not part of the contest) is static. But due to the placement of the colors, it appears to be rotating (Credit: Dennis Sylvester Hurd, /CC BY 2.0 /Wikimedia Commons)

The annual Best Illusion of the Year Contest encourages scientists and artists to showcase their ingenuity by creating clever optical illusions. Now celebrating its seventeenth year, the fun contest is the brainchild of the Neural Correlate Society, a nonprofit that promotes scientific research on how the brain functions. Here are 2021's top three winners, selected by fans from the ten finalists in an online vote on December 15, 2021.