Surprisingly, it’s not due to our conscious mind!
In a new study from KU Leuven, experimental psychologist, Vebjørn Ekroll, and colleagues describe the underlying principles of how our visual system processes the perceptual illusion known as the ‘Shrunken Finger Illusion.’ Their findings indicate that the completion effect of the illusion is due to our visual system filling in missing gaps, and not the conscious mind.
Magic tricks and illusions have long captured the interest of many psychologists. They provide the opportunity to comprehend how the brain processes visual information and gain insight into the brain’s remarkable ability to fill in missing gaps, allowing a complete perceptual experience.
During a previous study in 2013, Vebjørn Ekroll and his team, used magic tricks to show how our eyes fill in visual information, even if it’s known to be missing. The classic ‘multiplying balls’ routine used by magicians makes use of the perceptual illusion Ekroll’s team of psychologists described in their earlier work.
Illusions can get really strange sometimes, like the ‘Hole in Your Hand’ illusion, where a hole appears in the palm of your hand as your brain and visual system try to compensate, creating a completed perceptual experience with rather strange effects!
In their latest study, Ekroll and his colleagues looked at the ‘Shrunken Finger illusion’:
What happens when you rest a half chopped ping pong ball on your finger and look at it from above?
Their study found that our visual system fills in the bottom part of the ping pong ball, even if we know that it’s not there. This also made the finger the ping pong ball was resting on seem unusually short, to compensate for the ‘complete’ ball as illustrated in the drawing above.
“We already know that our mind completes what we don’t see”, Ekroll explained in a press release. “Our study shows that our visual system is behind the illusion, not our conscious mind. Rationally, we know that our finger is not actually shorter, but the illusion persists nonetheless.”
Their findings were published in Current Biology.
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