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Today I saw an optical illusion that I absolutely loved, to the point that I actually fired up IDL and generated my own set of animated gifs for this blog. Look at these two dots:

It’s easy to see that they are completely in phase and always the same colour. If we now place a big black border around one point and a big white border around the second point then something incredible happens:

The colours look like they’re completely out of phase, but really both of the dots are always the same colour as each other! No I don’t expect you to believe me. Yes you can go and check in Photoshop (or by hiding the image with a piece of paper then cutting two holes where the changing circles are). Here is a quote from Shapiro et al (2004), where this effect was first published:

The effect arises, in part, because of the conflict between the luminance and contrast signals. If our perception tracks the luminance level of the disks, then the disks should appear to be modulating in phase; if our perception tracks the contrast signal, which arises at the edge, the disks should appear to be alternating. Because at low frequencies both aspects can be perceived, the effect indicates that at a relatively late stage of visual processing, the signals that originate from the center of a patch of light can be separated perceptually from signals that originate at the edges. (p. 460)

This boils down to there being a conflict in the brain between the changing luminescence of the patches, and the contrast around their edges. Whatever it is, my mind is pretty much 100% blown

found via (Mixing Memory)

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