Paul Zak, a “neuroeconomist,” studies why we humans like and trust each other. And the answer, he’s found, is the compound oxytocin. In this photo, he’s brought a syringe loaded with the stuff onstage, and he creates a striking visual aid (and an outbreak of love and trust among the backstage crew) by atomizing it into the air. Photos: James Duncan Davidson / TED. Photo editor: Mike Femia

PS: Zak, who’s sometimes known as “Dr. Love,” also shared his prescription for nonchemical happiness: the hug, at least 8 a day. As he steps offstage, he gets a dose from TEDGlobal host Bruno Giussani.