How we forecast our feelings, and whether those predictions match our future emotional states, had never been the stuff of laboratory research. But in scores of experiments, Gilbert, Wilson, Kahneman and Loewenstein have made a slew of observations and conclusions that undermine a number of fundamental assumptions: namely, that we humans understand what we want and are adept at improving our well-being — that we are good at maximizing our utility, in the jargon of traditional economics. Further, their work on prediction raises some unsettling and somewhat more personal questions. To understand affective forecasting, as Gilbert has termed these studies, is to wonder if everything you have ever thought about life choices, and about happiness, has been at the least somewhat naive and, at worst, greatly mistaken.

SUSAN FISKE: Can we become more accurate in affective forecasting?

DANIEL GILBERT: Probably, but first we should ask whether or not we want to. It's very easy to see somebody making a logical error and say, "Well, you ought not to have made it." But logical errors can serve an important purpose in human cognition. Imagine a world in which some people realize that external events have much less impact than others believe they do. Those who make that realization might not be particularly motivated to change the external events. But one of the reasons we protect our children, for example, is that we believe we would be devastated if they were harmed or killed. So these predictions may be very effective in motivating us to do the things we as a society need to do, even though they might be inaccurate on an individual level. Anyone who wanted to cure affective forecasters of their inferential ills would be wise to measure both the costs and benefits of forecasting errors.

People are generally unaware of the operation of the system of cognitive mechanisms that ameliorate their experience of negative affect (the psychological immune system), and thus they tend to overestimate the duration of their affective reactions to negative events. This tendency was demonstrated in 6 studies in which participants overestimated the duration of their affective reactions to the dissolution of a romantic relationship, the failure to achieve tenure, an electoral defeat, negative personality feedback, an account of a child's death, and being rejected by a prospective employer.