Using an iPhone app called trackyourhappiness, psychologists at Harvard contacted people around the world at random intervals to ask how they were feeling, what they were doing and what they were thinking. The “Track Your Happiness” app periodically pings you throughout the day, asking you to fill out a quick survey. It asks how happy you are, what you’re doing at the moment, whether you exercised recently, whether you’re alone, and whether your mind is either wandering or in the moment. The latter question proved to be the key to the study, which concluded that a main cause of a person's unhappiness is how frequently his or her mind wanders. According to the app, 46.9 percent of people’s time is spent thinking about something other than what they’re doing. (Unless they’re having sex—the one activity where people reported mind-wandering less than 30 percent of the time.) And using a bit of statistical wizardry, study authors Matthew Killingsworth and Daniel Gilbert were able to tease out that that mind-wandering was in fact the cause of much of the reported unhappiness. It seems what activity a person was engaged in only accounted for about five percent of a person’s happiness, whereas whether that person’s mind was on- or off-task accounted for more than 10 percent. “A wandering mind is an unhappy mind,” the researchers determined.