Where the term comes from

The psychologists Timothy Wilson and Daniel Gilbert studied affective forecasting from the late 1990s. A 1998 paper called the error about duration a durability bias, and a 2002 chapter named the wider pattern the impact bias. Their 2005 review concluded that people usually predict correctly whether an event will feel good or bad, but misjudge how strong the feeling will be and how long it will last.

What the research shows

In a housing lottery at Harvard, first-year students predicted how happy they would be a year later in each of the residential houses they might be assigned to. Those sent to a house they had expected to dislike predicted 3.43 on a 7-point scale and reported 5.38; those who got a house they wanted predicted 5.96 and reported 5.45, no happier than the first group. The students had weighed physical features such as location over the social life that turned out to matter more. Losses show the same pattern: people expected a lost gamble to hurt more than an equal win would please, but the loss hurt less than they had predicted.

Where the evidence stops

Part of the bias may come from how it is measured. In a 2012 set of studies, people predicted their feelings about an election result or an exam grade accurately; they overestimated only when asked about their general mood, which most took to mean their feelings about the event. The impact bias is the research finding behind the popular idea of the arrival fallacy, while the hedonic treadmill describes the adaptation that follows a change. Why success feels empty shows how both play out after a major milestone.

Related terms

Arrival Fallacy: the popular name for this error when the event is a long-chased goal.

Hedonic Treadmill: the adaptation that follows a good or bad change.

Post-Achievement Depression: an everyday name for low mood after a big win.