"In his book, "Thinking, Fast and Slow," Nobel Prize-winning economist Daniel Kahneman mentions an experiment in which subjects were shown three words and were given two seconds to guess if they were linked. "Putting the participants in a good mood ... more than doubled accuracy," Kahneman writes. Unhappy subjects, on the other hand, made guesses that were no better than random. This is not to dismiss everything else we use to fill our brains. The Internet is a tool for thinking. So are meetings, mystery novels, video games and quiz shows, for that matter. And sometimes thinking has to be done on the fly. Impending deadlines, to paraphrase Samuel Johnson's line about the prospects of being hanged, can focus the mind wonderfully. But perhaps the best tool is time alone, feet up on the desk, staring at the ceiling." - × × ×