There seems to be a major uncontrolled variable in this study, namely external expectations of what you <i>should</i> be doing.<p>I found, as a kid up through college, that I was happiest when my mind was wandering. As a kid, I also had no expectations about what I should be doing - I basically decided that homework was bullshit as a young teen, so I could do whatever I wanted and not feel guilty about it.<p>That changed once I got into the working world and suddenly was responsible for my own success. Now, whenever my mind wanders, there's a little voice that goes off in my head and says "But you're not being <i>productive</i>! Nobody cares what you think about, they only care what you do."<p>It seems like a reasonable hypothesis to say "people are happiest when they're doing whatever their internal value system says they should be doing." And it's consistent with the data. People were least happy when resting, working, and using a home computer, which are also the times that social expectations are highest that you actually <i>should</i> be working. They were most happy when having sex, exercising, and conversing - but nobody expects you to do a job while having sex.<p>I'd like to see the data broken down by age group and cultural values, and in particular, I'd like to see if it holds true for cultural groups that do not have the same focus on productivity and achievement as middle-class Americans.