Chimps Will Work Harder to Get Their Favorite Foods Read more: http://www.smithsonianmag.com/smart-news/chimps-will-work-harder-get-their-favorite-foods-180954618/#7wvdtWS5oB5iOGly.99 Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv Follow us: @SmithsonianMag on Twitter
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Story in the Smithsonian by Marissa Fessenden
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