Daydream believer

"If your mind didn't wander, then you'd be largely shackled to whatever you are doing right now," says Jonathan Schooler, a psychologist at the University of California. "But instead you can engage in mental time travel and other kinds of simulation. During a daydream, your thoughts are really unbounded."

According to Schooler there are two types of daydreamer. The first doesn't notice they are day dreaming, the second does. Its this second type that tend to have break through ideas. "The point is that it's not enough to just daydream," he says. "Letting your mind drift off is the easy part. The hard part is maintaining enough awareness so that even when you start to daydream you can interrupt yourself and notice a creative insight."

He cites the example of Minnesotan engineer Arthur Fry who, in 1974, was sat in church, pondering how to insert scraps of paper into his choir book, so that he could quickly find the right hymns during the service. Instead of listening to the sermon, he let his mind wander. "It was during the sermon," he said "that I first thought, 'What I really need is a little bookmark that will stick to the paper but will not tear the paper when I remove it.' " And so was born the Post-It Note.