New Scientist reports on an unusual perceptual quirk schizophrenia grants its victims – the ability to see through the tricky “hollow mask” optical illusion:
Telling the front from the back of a mask can be more difficult than it seems. Thanks to an effect called the hollow-mask illusion, the brain can have trouble deciding if the image is convex or concave.
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In the study, volunteers were monitored in an fMRI (functional Magnetic Resonance Imaging) scanner as they looked at photos. Some of these were normal pictures of faces, but others had been inverted as in the hollow-mask illusion. All the participants with schizophrenia could distinguish between the two types of photos, whereas control volunteers without the condition were fooled 99 per cent of the time.
You can read more about the University of Hannover study at NeuroImage.
The researchers say it’s because of a difference in what they call “top-down” processing – the way brains match things in the environment to what they expect to see. I think that has to do with the way our brains “like” seeing faces – the same reason why we’re inclined to find the Virgin Mary in tree stumps or a man (or woman) in the moon.