After 11 years of study, Oxford University Professor Michael Argyle says he knows what makes people happy. It isn't being rich: "Satisfaction and happiness do not increase with income," he says. The key to happiness, rather, is marriage, and the least happy are the divorced and separated. But don't have an affair: that can ruin the marriage, the basis of happiness.

"Having two people who give you support and company could be a good thing. But it rarely works out that way," Argyle cautioned. There is an alternative to marriage, though: people addicted to TV soap operas also tend to be happy. "The results on television watching have been most perplexing," he said. "One theory is that through doing it, they are making imaginary friends."