How do humans gain power? By sharing it

In the past, violence was the quickest route to establishing dominance. But today, people gain influence by advancing the welfare of others, according to psychologist Dacher Keltner. The more power people derive from helping others, however, the more likely they are to prioritize selfishness over altruism -- leading to what Keltner calls a ‘power paradox.’ Economics correspondent Paul Solman reports.