If all goes to plan, this blog post will hopefully serve two functions. First, I hope to introduce you to what I consider to be a rather cool illusion related to face perception. Second, it will serve as a forum for me to vent my frustration at having recently discovered a research idea of mine has already been published in a prestigious journal.
In my spare time of late I’ve been perusing the face perception literature. It has been well documented that presenting a face upside-down dramatically affects its recognition. So much so that you may even mistake the identity of the image for someone else. You may have experienced this for yourself perhaps when looking at a paper that someone else is reading from across the table. Initially the person on the front cover is difficult to recognise. “Who is that you think? Is that that creature from Lord of the Rings?” Upon snatching the paper from your friend and reorienting the image you realise you were mistaken and it is in fact Tony Abbott.
Without going into too much detail, this effect is thought to be the result of psychological processes involved in face perception that are tuned specifically to upright faces. A slightly more striking illusion that is thought to illustrate these same cognitive processes is the “Thatcher illusion”. The Thatcher illusion shows that it is difficult to detect local feature changes in an upside down face, despite identical changes being blindly obvious in an upright face. So what on earth does that mean? I’ll let the illustration below do the explaining.
The first image is of my adolescent crush Elisha Cuthbert. The second image is the same as the first except the eyes and the mouth have been inverted. Looks grotesque yes? The last image is one of the first two images upside-down, any guesses which one it is? The animation below should reveal the answer for you.
The illusion itself has been well documented. Where I thought I stumbled across something of interest was in looking at the angle of rotation at which the image appears to change from an “intact” face to a deformed image. Of those I’ve shown this to, some report a gradual change from one image to the other while others have report a sudden switch. Personally my perception of the image seems to flip when the rotation reaches a critical angle just beyond 90 degrees.
Alas, it would seem that this line of thought has already been investigated and I must return to the drawing board...
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