Psychologist Barry Schwartz takes aim at a central tenet of western societies: freedom of choice. In Schwartz's estimation, choice has made us not freer but more paralyzed, not happier but more dissatisfied.

In this prescient 2005 talk, Clay Shirky shows how closed groups and companies will give way to looser networks where small contributors have big roles and fluid cooperation replaces rigid planning.

At the 2007 EG conference, Kevin Kelly shares a fun stat: The World Wide Web, as we know it, is only 5,000 days old. Now, Kelly asks, how can we predict what's coming in the next 5,000 days?

Armed with a sense of humor and laypeople's terms, Nobel winner Murray Gell-Mann drops some knowledge on TEDsters about particle physics, asking questions like, Are elegant equations more likely to be right than inelegant ones?

First, Keith Barry shows us how our brains can fool our bodies -- in a trick that works via podcast too. Then he involves the audience in some jaw-dropping (and even a bit dangerous) feats of brain magic.

"Rock-star physicist" Brian Cox talks about his work on the Large Hadron Collider at CERN. Discussing the biggest of big science in an engaging, accessible way, Cox brings us along on a tour of the massive project.

Positive psychologist Martin Seligman talks about psychology -- both as a developing field of study, and as it works one-on-one with each patient and each practitioner. As it moves beyond a strict focus on curing mental disorders and dis-ease, what can modern psychology help us to become? (Recorded February 2004 in Monterey, California. Duration: 23:41.)

Why do we crave love so much, even to the point that we would die for it? To learn more about our very real, very physical need for romantic love, Helen Fisher and her research team took MRIs of people in love -- and people who had just been dumped.

Nine days before TED2008, filmmaker David Hoffman lost almost everything he owned in a fire that destroyed his home, office, and 30 years of passionate collecting. He looks back at a life that's been wiped clean in an instant -- and looks forward.

With 50 million views since we started posting video two years ago, TEDTalks have become a powerful cultural force.