Impact bias
Overestimating how intensely and how long future events will move us.
What it means
The impact bias is the systematic tendency, in affective forecasting, to overestimate both the intensity and especially the duration of one's emotional reactions to future events. Two mechanisms are central: focalism (or the focusing illusion), in which we dwell on the emotional event in isolation and neglect the many other things that will also fill our days and dilute its impact, and immune neglect, our failure to anticipate the 'psychological immune system' of rationalization and adaptation that quietly restores equanimity. Because of these, both good and bad events fade far faster than we predict, so windfalls thrill less durably and setbacks wound less lastingly than imagined. A noted boundary is that the bias is strongest for duration and for major, attention-grabbing events, while predictions of the immediate direction and rough intensity of feeling are often roughly right. It matters because these forecasting errors steer momentous decisions — career moves, relationships, major purchases, medical choices — toward whatever we believe will make us happiest, even though our predictions about lasting happiness are unreliable.
Examples
Both lottery winners and people who suffer serious accidents tend to drift back toward their earlier baseline level of happiness within a year or two, far sooner than either group would have predicted.
The promotion you were certain would change everything is background noise within a month. The commute, the deadlines and the dull meetings crowd straight back in, exactly as before.
Students predict that rejection from their first-choice university will blight the whole year. By the following term most are as happy as ever, for reasons they never thought to forecast.
First described in Gilbert, Wilson and colleagues (1998).