Why does time fly?

Another paper in the August issue of Psychological Science, this one by Gable and Poole, looks at the conditions under which time flies while we're having fun. Their hypothesis is that approach motivations result in shorter perceived time intervals. Approach motivations? Well, one way of thinking about goals and motivations is like vectors, with some moving towards your goal and some moving away from them. You know, I like to approach a slice of chocolate cake, but avoid the dentist at all cost (I know it may ultimately be impossible to do both, but that's a question of intertemporal choice, which we'll get to some other time). In three experiments, they show that "positive approach motivation" (that is, you feel good about moving towards a goal) speeds up the perception of time, and the stronger the approach motivation, the faster time is sped up (within limits of course). That's all interesting, but what I really liked about the paper was their potential explanation for why positive approach motivations (let's just call them "fun") makes time fly. I'll quote the article:

Reduced perceptions of time may assist in abating irrelevant processes that would delay or hinder goal acquisition. (p. 6)

In other word, by shortening our perception of the time it takes to achieve whatever goal we're approaching (say, getting a piece of cake), we're less likely to get distracted and deviate from the path to the goal. I'm looking forward to future studies testing this hypothesis directly.