Jillian Blenis, 30, of Boston reacts while stopping at a makeshift memorial to marathon bombing victims Wednesday. Julio Cortez/AP hide caption

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Researchers say that aggressive people tend to interpret ambiguous faces as reflecting hostility. hide caption

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When anthropologists tallied the use of emotional words through a century of literature, they included many books without clear emotional content — technical manuals, for example, and automotive repair guides. Steve Debenport/iStockphotography hide caption

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Samantha Grimaldo was born with a rare disorder, Perisylvian syndrome, and has never been able to speak. Ellen Webber for NPR hide caption

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For some kids who grow up in poverty, the bond developed with Mom is especially important in dealing with stress. hide caption

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Notice anything unusual about this lung scan? Harvard researchers found that 83 percent of radiologists didn't notice the gorilla in the top right portion of this image. Trafton Drew and Jeremy Wolfe hide caption

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Could you say "no" to this face? Christoph Bartneck of the University of Canterbury in New Zealand recently tested whether humans could end the life of a robot as it pleaded for survival. Christoph Bartneck hide caption

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People visit a memorial outside Sandy Hook Elementary School in Newtown, Conn., on Dec. 15. Spencer Platt/Getty Images hide caption

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A Hare Krishna distributes food gifts from a chariot during a festival in London in 2011. The religious group began distributing books, flowers and gifts to strangers in the 1970s, drawing on the rule of reciprocation to raise money. Matthew Lloyd/Getty Images hide caption

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Chinese schoolchildren during lessons at a classroom in Hefei, east China's Anhui province, in 2010. STR/AFP/Getty Images hide caption

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Jennifer Ruiz and her 2-year-old daughter, "Moo Moo," at a Red Cross shelter in Little Egg Harbor Township, N.J. Ruiz and her daughter evacuated from their home in Seaside Heights. Alix Spiegel/NPR hide caption

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With the advent of radio and television, presidential charisma became a more important personality characteristic. Above, Franklin Delano Roosevelt, who is rated one of the most charismatic presidents; John F. Kennedy; Bill Clinton. Getty Images hide caption

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