Impact Bias

What it is

Many choices are made for the sake of a feeling. People take a job for the pride it will bring, move house for the relief, avoid a risk for the regret they expect to escape. Each of these is a prediction about a future emotional state, and the research on affective forecasting asks how good the predictions are.

Wilson and Gilbert's 2005 review in Current Directions in Psychological Science reports that people tend to overstate how intense their future feelings will be and how long they will last. The pattern is called the impact bias, and the review says it is strongest for negative events. It names two causes.

The first is focalism. When a person imagines an event, the event fills the picture, and the other things that will happen and will shape how the person feels are left out. The imagined event is the only thing in the frame, so its effect is overweighted.

The second is a failure to foresee how quickly people make sense of what happened. People recover from setbacks partly by making sense of them, and the process speeds up recovery. A forecaster who does not anticipate it expects the feeling to last longer than it does. The review also notes that people tend to credit their unexpected resilience to external factors.

The finding bears on any practice that involves imagining a result and its feel. A mental rehearsal of a decision usually contains a scene of the result, and the scene carries an implicit forecast of how it will feel. The review does not test rehearsal as a technique. It describes what imagined futures tend to leave out.

In effect

In decisions about the future

For instance, a person deciding whether to take a post in another city may imagine the day of arrival, and the imagined day carries the pleasure or the dread. The review's account suggests that the forecast is biased towards the strong, long version, and that it leaves out the ordinary weeks that will follow.

In rehearsal

A vivid scene of the result adds detail to the forecast without correcting it. The use the review suggests, and the inference here is ours, is to ask of any rehearsed scene what else will be happening in the period in which the decision takes effect.

In the vault

Timothy Wilson and Daniel Gilbert also appear in the article on why ten quiet minutes feel so long, which concerns what people do with unfilled thinking time. That work and this one share an interest in how poorly people predict their own experience.

What it does not say

It does not say forecasts are always too strong. The review describes a tendency, strongest for negative events, and not a law.

It does not say that a person cannot learn to forecast better. The review is a description of the typical pattern.

It does not test mental rehearsal. Its subject is predictions of feelings, and the link to rehearsal on this page is an inference.

The vault has not run a search for the research that disputes the size of the effect or the measures used, and this page should be read with that gap in mind. Its originator line is recorded with low confidence, because the term has an earlier history that has not been traced here.

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