9319558 GILOVICH ABSTRACT Previous research indicates that people experience more regret over negative outcomes that stem from actions taken than over identical outcomes that stem from actions foregone. For example, someone who loses money by selling stocks to buy another one is believed to regret the loss more than someone who thinks about switching but hangs onto his or her current stock. As compelling as this might seem, it conflicts with an observation from everyday life: when people describe what they regret most, their regrets often center around things they failed to do. The purpose of this research is to further our understanding of regret by reconciling everyday observation with the results of previous research. The research has three objectives. The first is to verify everyday observation. Do omissions in fact predominate in the biggest regrets of people's lives? A series of structured interviews will ascertain the most common regrets in people's lives. The second objective follows from the first. If people's biggest regrets involve things they failed to do in their lives, how can we account for previous research that demonstrates the opposite result? This research will explore whether there is a systematic time course to the experience of regret: people regret their unfortunate actions more in the short term (as current research suggests), but their unfortunate inactions more in the long run (as everyday experience suggests). An experimental test of this proposed temporal pattern will be conducted. The third objective is to understand why this temporal pattern might exist. In particular, a series of laboratory experiments will examine: 1) why regret over action tends to diminish with time, 2) why regret over inaction tends to intensify with time, and 3) why our regrettable inactions remain more cognitively available to us in the long run. By furthering our understanding of the regret, this research promises to improv e everyday judgement and decision making. In addition, the examination of underlying mechanisms should expand our knowledge of basic social psychological phenomena such as post-decision dissonance reduction, subjective confidence, and counterfactual thinking.