Impact bias

"When we think about how we will react to possible future events, we tend to overestimate both the intensity and duration of our emotions."


We are always trying to predict the future because predictions help guide our behaviour. Some of our predictions, known as “affective forecasts”, are about how we will feel if future events occur. Like all predictions, people’s affective forecasts often involve errors. The most common error is known as the “impact bias”, which is the tendency people have to overestimate the impact that future events will have on their emotional experience [1]. The term “impact” refers to both the intensity, and the duration of anticipated emotional experiences. When anticipating positive events, such as retirement, or the birth of a child, people often expect to feel happier, and for a longer period of time than is actually likely. Likewise, people often overestimate the intensity and duration of negative emotions when thinking about negative future events, such as an HIV diagnosis, being insulted by a co-worker, or going through a divorce. The effect has been demonstrated in a laboratory setting over the course of minutes or hours, and outside the lab across months or years.


When university students typically think about how happy they will be when they graduate, they tend to demonstrate the impact bias. That is, they tend to think they will be happier upon graduation (i.e., intensity), and that this happiness will last for weeks or even months (i.e., duration). In reality, the experience does not live up to students’ expectations – the happiness they feel is often mild and fleeting. Thus, the impact bias influences students’ perceptions of their future happiness upon graduation.


Researchers have identified two possible sources of this bias – heuristics and motivation. First, when thinking about the future, people use heuristics that sometimes result in less-than-perfect predictions. For example, people tend to focus more on features that are unique to possible future events, and less on aspects that these events share with other possible future events. When thinking about how you would feel if you got a sought-after promotion at work, you may focus more on features that are unique to this event (e.g., increased salary, new office) than on features that this event has in common with other events, such as not getting the promotion (e.g., daily commute, same co-workers). This is known as the “isolation effect”, and is just one of several heuristics than can influence the accuracy of our predictions [1]. This heightened focus on unique aspects of future events makes the impact bias more likely to occur because our mental representation of a future event is not representative of the actual event.

More recently, some research suggests that the source of the impact bias may also be motivational [3]. When a person is looking forward to a future event (e.g., graduation), overly high expectations of how they will feel may motivate them to strive to make this event a reality (e.g., studying harder). Likewise, over-anticipation about a possible negative event (e.g., getting fired) could facilitate behaviours that make the occurrence of this event less likely (e.g., working harder). Thus, the impact bias may exist partly as a result of motivational underpinnings – as a means to assist in goal-striving.


The consequence of the impact bias is clear – people tend to overestimate their emotional reactions to future events. However, it is unclear whether people would be better with or without it. Although expectations about future emotions may not be fully accurate, this bias may promote goal-directed behaviour, making the attainment of future goals (and avoidance of negative outcomes) more likely.

Thoughts on how to act in light of this bias

  • Consider asking other people how they think that you will feel. Adopting an outside perspective can offer a more objective outlook on your emotional reactions to future events.

  • Trying to improve the accuracy of an imagined scenario could reduce the effects of some cognitive errors (e.g., spending more effort imagining the scenario).

  • Practicing gratitude can bring actual experiences closer in line with predicted experiences by allowing us to more strongly appreciate what we have in the present.

How is this bias measured?

Traditionally, the impact bias has been observed by measuring predicted, and then actual emotional reactions to events. For example, researchers asked incoming first-year university students how happy they would be one year from now if they were able to live in various university dorms, some of which were rated as more desirable than others [2]. Not surprisingly, students expected to be happier if they were assigned to live in the desirable dorms. However, one year later, researchers asked these students how happy they actually were and found no significant difference in happiness between students living in desirable and undesirable dorms. Here, the impact bias led students to overestimate the influence that living in various dorms would have on their happiness at university. If the impact bias was not present, we would expect students’ predictions to more closely reflect reality.

This bias is discussed in the scientific literature:


This bias has social or individual repercussions:


This bias is empirically demonstrated:



[1] Wilson, Timothy D. & Daniel T. Gilbert (2003). Affective forecasting. In M. P. Zanna (Ed.), Advances in experimental social psychology (Vol. 35). San Diego, CA: Academic Press.

[2] Dunn, Elizabeth, Timothy D. Wilson & Daniel T. Gilbert (2003). Location, location, location: The misprediction of satisfaction in housing lotteries. Personality and Social Psychology Bulletin, 29(11), 1421-1432.

[3] Morewedge, Carey K. & Eva C. Buechel (2013). Motivated underpinnings of the impact bias in affective forecasts. Emotion, 13(6), 1023-1029.


Individual level, Emotional heuristic, Need for cognitive closure

Related biases

  • Focalism 

  • Distinction bias


Myles Maillet is a Ph.D. Candidate (Social Psychology) at the University of Victoria. He is also a statistical consultant, data analyst, and sessional instructor at both the University of Victoria and at Vancouver Island University. His research focuses on motivation, self-regulation, and why it can be hard to manage temptations and challenges when striving towards our goals.

How to cite this entry

Maillet, M. (2020). Impact bias. In C. Gratton, E. Gagnon-St-Pierre, & E. Muszynski (Eds). Shortcuts: A handy guide to cognitive biases Vol. 1. Online:

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