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Leafsnap app; best visual illusion of the year

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An app that didn’t fall far from the tree

Leafsnap

No more lugging around nature guidebooks on hikes: iPhone users can download Leafsnap, a free app that identifies tree species from photographs of their leaves. Take a photo of a leaf against a plain white background and the app will tell you which species of tree it probably belongs to.

Users can see photos of the tree’s branches, flowers, fruit and bark to double-check the accuracy. Leafsnap was developed by researchers at the Smithsonian Institution, University of Maryland and Columbia University. The app includes the species of Washington and New York, but its developers plan to expand to the entire country.

It’s true: You can’t believe your eyes

2011 Best Illusion of the Year contest

In great optical illusions, straight lines bend, dots disappear and 3-D images pop out of seemingly 2-D drawings. Jordan Suchow and George Alvarez of Harvard University created an illusion called “Silencing awareness of change by background motion,” which just won the title “Best Illusion of the Year.”

In the 14-second video, bright dots that form a ring around a tiny white dot change colors. When the ring starts to rotate, the dots appear to stop changing color; in reality, they are changing the whole time, but our eyes can’t detect it.

A nonprofit called the Neural Correlate Society has hosted the annual contest since 2005. View the year’s top 10 illusions at www.illusioncontest.neuralcorrelate.com.

— Rachel Saslow

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