The author gave a TED talk about this here: https://www.youtube.com/watch?v=Qy5A8dVYU3k
and yes, the default mode of the mind is to wander: http://en.wikipedia.org/wiki/Default_mode_network
and yes, the default mode of the mind is to wander: http://en.wikipedia.org/wiki/Default_mode_network
The difference is about 10%, it might be a very solid 10% more happy, but god, scratching my back can make me 10% more happy :-D