Having a perfect memory can put a strain on relationships, because every slight is remembered. Katherine Streeter for NPR hide caption

itoggle caption Katherine Streeter for NPR

Ellie is a computer simulation designed to engage real people in meaningful conversation and take their measure. The computer system looks for subtle patterns in body language and vocal inflections that might be clues to underlying depression or other emotional distress. YouTube hide caption

itoggle caption YouTube

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

itoggle caption Julio Cortez/AP

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

itoggle caption iStockphoto.com

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

itoggle caption Steve Debenport/iStockphotography

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

itoggle caption Ellen Webber for NPR

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

itoggle caption iStockphoto.com

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

itoggle caption Trafton Drew and Jeremy Wolfe

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

itoggle caption Christoph Bartneck

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

itoggle caption Matthew Lloyd/Getty Images