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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Pathologist Thomas Harvey took dozens of photos of Einstein's brain. This one shows that Einstein's prefrontal cortex (associated with higher cognition and memory) is unusually convoluted. On the right side of the brain there are four large ridges, where most people have only three. Brain(2012)/National Museum of Health and Medicine hide caption

itoggle caption Brain(2012)/National Museum of Health and Medicine

Among common health problems, depression was linked to the highest increase in annual spending by employers' on workers' health care. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Is there an angel or a devil behind the mask? Scientists say it may not matter in terms of anonymous behavior. Joel Saget/AFP/Getty Images hide caption

itoggle caption Joel Saget/AFP/Getty Images