Infidelity is the ultimate betrayal. But does it have to be? Relationship therapist Esther Perel examines why people cheat, and unpacks why affairs are so traumatic: because they threaten our emotional security. In infidelity, she sees something unexpected — an expression of longing and loss. A must-watch for anyone who has ever cheated or been cheated on, or who simply wants a new framework for understanding relationships. TEDTalks is a daily video podcast of the best talks and performances from the TED Conference, where the world's leading thinkers and doers give the talk of their lives in 18 minutes (or less). Look for talks on Technology, Entertainment and Design -- plus science, business, global issues, the arts and much more. Find closed captions and translated subtitles in many languages at www.ted.com/translate Follow TED news on Twitter: www.twitter.com/tednews Like TED on Facebook: www.facebook.com/TED Subscribe to our channel: www.youtube.com/user/TEDtalksDirector