When it comes to nature versus nurture, brain scientists think both matter. Daniel Horowitz for NPR hide caption

itoggle caption Daniel Horowitz for NPR

Police officials stand next to a bullet-ridden Seattle Metro bus on Aug. 12. A man with a history of mental illness shot and wounded the driver, then died in a chaotic shootout with police. Ted S. Warren/AP hide caption

itoggle caption Ted S. Warren/AP

Flags fly at half-staff Tuesday after the deadly shootings at the Navy Yard in Washington, D.C. J. Scott Applewhite/AP hide caption

itoggle caption J. Scott Applewhite/AP

Beer pong and other drinking games are popular among teenagers, and play a role in binge drinking. iStockphoto.com hide caption

itoggle caption iStockphoto.com

I told him he would break his arm if he did that. But he did it anyway. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Strenuous mental exercise like reading difficult books, solving tricky math problems — or, maybe, playing the right video game — can help keep a healthy brain sharp, research suggests. Images.com/Corbis hide caption

itoggle caption Images.com/Corbis

Beautiful or creepy? A recent survey found that an image of a lotus seed head makes about 15 percent of people uncomfortable or even repulsed. tanakawho/Flickr.com hide caption

itoggle caption tanakawho/Flickr.com