This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
The surrounded circle looks larger than the isolated circle, even though both black circles are identical.
http://commons.wikimedia.org/wiki/File:Dentist_extracting_tooth..JPG
If you’re a bit lax with your post-holiday brushing, this little-known illusion may give you the incentive you need to keep those candy canes in check, or at least brush and floss afterwards. Vision scientist
Robert O’Shea and his colleagues published a recent study in
PLoS One showing that dentists can fall prey to a visual illusion of size and make larger holes in teeth than needed.
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http://commons.wikimedia.org/wiki/File:First_visit_to_the_dentist.jpg
The illusion fooling the dentists is a variant of a classical perceptual phenomenon known as the
Delboeuf illusion, named after its creator, the Belgian natural philosopher, experimentalist, mathematician and hypnotist Joseph Remi Leopold Delboeuf.
http://commons.wikimedia.org/wiki/File:Dentist%27s_sign,_Hillsborough_-_geograph.org.uk_-_1591235.jpg
The scientists supplied 8 specialist dentists and endodontists, who served as experimental subjects, with a large pool of extracted teeth. The teeth contained holes, and the task of the dentists was to cut cavities in preparation for filling. Unknown to the dentists, each tooth presented a more or less powerful version of the Delboeuf illusion, making the holes appear smaller than their actual size. The results showed that the smaller the holes looked, the larger the cavities that the dentists made for later filling. The researchers recommend that dentists and other health practitioners receive training in “illusion awareness” (my words, not theirs), so that they may counteract these and related perceptual effects.
READ ABOUT OTHER SIZE ILLUSIONS HERE>>>
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