Here's the illusion: pic.twitter.com/thNAPQLZlk— Steven Pinker (@sapinker) January 16, 2018
Look carefully at the coloring on the lines. On one set of pairs the coloring alternates between peaks and troughs; on the other set it alternates between the slopes. Though the wave forms are exactly the same for these pairs, they're perceived differently against the medium gray background.
Excellent new visual illusion by Kohske Takahashi: shows how the brain seeks an interpretation of the retinal input with the simplest combination of 3D shape, surface pigmentation, & illumination. //www.newsweek.com/psychology-neuroscience-optical-illusions-744675— Steven Pinker (@sapinker) January 16, 2018