Can You Help Me Tie My Shoe? Researchers found that when study participants were asked an unusual request, they were more likely later on to perform a favor. iStockphoto.com hide caption

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Researchers studying brains want to know what's happening in an area called the premotor cortex — the place in the brain that gears up for something the body is about to do, like swimming. Above, Michael Phelps dives off the starting blocks in the final heat of the men's 400-meter individual medley during the 2012 U.S. Olympic Swimming Team Trials in Omaha, Neb., on June 25. Jamie Squire/Getty Images hide caption

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A 3-D model of HIV peeled back to show its layers. HIV's genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike. Courtesy of Ivan Konstantinov/© Visual Science 2011 hide caption

itoggle caption Courtesy of Ivan Konstantinov/© Visual Science 2011

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/via Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/via Wikimedia Commons

New York Winemaker Christopher Tracy and a bottle of his Blaufrankisch. The wine's difficult to pronounce name may attract oenophiles. Charles Lane/NPR hide caption

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Data from the Twins Early Development Study shows areas in the U.K. where the effect of environmental factors, shown in pink, trumps the influence of genes, shown in blue, and vice versa. TEDS hide caption

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Susan Backlinie swims as the great white shark rises toward her in publicity art for the 1975 film Jaws. Universal/Michael Ochs Archives/Getty Images hide caption

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Unrefrigerated brains in preserving solution are stacked high on shelves at the Harvard Brain Tissue Resource Center at McLean Hospital. Olin College of Engineering/Flickr hide caption

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Cockroaches have hooks on their back legs that let them swing around surfaces onto the underside while running full-speed. YouTube hide caption

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Balinese government officials prepare to cull chickens as a precautionary measure to prevent the spread of bird flu at a market in Denpasar on April 26. Firdia Lisnawati/AP hide caption

itoggle caption Firdia Lisnawati/AP