An curved arrow pointing right. A popular illusion online has people scratching their heads. The trick involves taking one giant chocolate bar, cutting it into pieces, and shifting them around ...

The illusion has gone viral across social media ... but this is only due to the surrounding hair color and background shading,' it explained in the caption. 'When placed together, you'll see ...

so some assumptions are made in order to maintain normal processing," the paper explained. "As a result, some scientists believe that optical illusions are caused by a lack of information or a ...