The Munker-White Illusion: flawed expectations of brightness and shadow.
Take a look at the grey areas. Is one darker? Which one? Take a look at the next image. Is the grey background darker than the grey box?
Oddly enough, this is somewhat of grey area itself in perceptual studies. It goes against what would be expected based on established theories. The grey in the black area should look lighter, not darker. The grey bars are the same luminance yet they elicit different perceptual brightness in our easily tricked minds. Light and dark perceptions have various components, such as expectations of shaded areas as demonstrated in the always perceptually rattling Cornsweet Illusion, seen below.
The blocks are the same shade of grey… Or, if you think back far enough to a few weeks ago, you may remember the heated debate of #thedress where some saw white and gold, and others blue and black. Some people may have been taking different cues from the spatial context of the dress in question.
Perception can be profoundly affected by spatial context. Context is everything. Surroundings can enhance or reduce contrast, as it does in the Munker-White Illusion and the Cornsweet Illusion demonstrated here. Beyond their entertaining aspects, illusions that elicit perceptual peculiarities give us tremendous insight into the fallibility of our senses. We can use them to further our understanding of those senses. This illusion has yet to be nailed down, but that hasn’t stopped anyone from trying.
Do you think you can figure it out, budding scientists out there? I entrust you with this responsibility. Happy perceptual hunting!
Li, Tavantzis, and Yazdanbakhsh (2009). Lightness of Munker-White illusion and Simultaneous-Contrast illusion: Establishing an ordinal lightness relation among minimum and split-frame presentations Review of Psychology, 16 (1), 3-8
Purves D, Shimpi A, & Lotto RB (1999). An empirical explanation of the cornsweet effect. The Journal of neuroscience : the official journal of the Society for Neuroscience, 19 (19), 8542-51 PMID: 10493754