In Kahnemann's chapter called "Two Selves" from Thinking, Fast and Slow, he discusses a very interesting bias having to do with how we feel about, value, or rate experiences having positive or negative attributes.
In a simple economic model, it would make sense to assume that a positive experience lasting 2 hours would be "worth" twice as much as a positive experience lasting only 1 hour.
Conversely, a negative or painful experience lasting 2 hours (or 2 months, or 2 years!) would be twice as bad as a negative or painful experience lasting only 1 hour (or 1 month, or 1 year).
One way to state this, is that if we were to graph painfulness vs. time, then it would make sense to say that the total negative impact of the pain should be the area under the curve.
But this is not so!
The mind is not wired to make such evenly weighted evaluations.
Redelmeier's and Kahneman's 1996 study of colonoscopy pain showed that the negativity of patients' experiences depends on how severe the pain of the procedure was at its peak, and on how painful the procedure was when it was ending. It DID NOT depend on how long the procedure lasted. Other research has shown similar results.
Therefore, if two painful events occur for an equal length of time, after which the pain of one of the events suddenly stops, while the pain of the other event gradually diminishes, people will rate the second event more favourably, because they experience gradual relief at the end of the event. This is even though the second event technically involves a larger total amount of pain (since the painfulness continues for a longer time).
Even if one painful event is much longer than another, it will be experienced in retrospect to have been more comfortable if the discomfort diminishes near the end. Similarly, a brief but intensely painful experience will have a more negative experiential impact compared to a much longer period of moderate painfulness.
As Kahneman shows so well, the mind exhibits "duration neglect"-- it tends not to calculate the goodness or badness of things according to adding up all the good or bad experiences over time. Instead, the mind attends to the very worst moment, and to the period of time which is most recent.
This bias could lead to a variety of problems in making healthy choices. A problem which causes gradual health deterioration over many years could be preferred to another problem which would cause much less long-term harm, but which would be acutely more uncomfortable. Addictions are an obvious example--the long term deterioration due to addictive behaviour may be barely noticeable, and quite tolerable in the moment. Even the cumulative effect of the harm (the "area under the curve") might not be attended to experientially. But acute withdrawal would be very uncomfortable, despite being much more favourable to long-term health.
In relationships, people might be tempted to stay in a chronically bad situation, if each time a severe problem occurs, there is a gentle apology or other positive relief afterwards. The mind preferentially attends to the end of episodes, so if the ending is "positive" it may cause us to view an overall negative experience as much more positive than it warrants.
Similarly, we may undervalue long-term positives, if the ending happens to deteriorate. A relationship which was thoroughly enjoyed in the moment every day for years might be remembered, and assimilated into retrospective experience, much, much more unfavourably if it ended in a negative way.
This touches on the human tendency to view and experience life as we would a novel or other narrative: we highly value the intense moments of the story, and we highly value the ending. If the story is long and enjoyable, but has a disappointing, weak, or negative ending, then we are likely to devalue the entire story.
What implications does this have for psychiatric therapy?
First, I think it is important to acknowledge this fact about how the mind is "wired." In a therapeutic environment, it may be especially important to work towards having positive endings to appointments if at all possible, particularly if there has been difficult or painful subject matter dealt with.
A converse point, one which I think Kahneman does not attend to very much in his work, is to consider whether the brain can be trained systematically to over-ride its biases. Kahneman at times seems resigned to assume that nothing can over-ride these phenomena, as for example he observed that his well-informed psychology student subjects were just as vulnerable to biases as anyone else. But Kahneman has not, in his current work, looked at ways to intensively train the mind to overcome specific biases. I suspect that, as with any skill, it would take hundreds of hours of deliberate, focused practice to have any chance to change an ingrained mental habit.
I am therefore curious to explore the possibility of re-evaluating the "weighting" of experience as a sort of cognitive-behavioural exercise. The mind tends to focus on peaks and endings, but perhaps through disciplined, prolonged mental effort (in a sort of CBT style), we could practice ways of emphasizing in our memory those points of experience between the peaks of pain, and before any endings. This idea resonates with a sort of "positive psychology" or gratitude-journal approach, but in this case specifically recognizing that our brains may over-attend to strong negatives, therefore we should work at bolstering our attention to other points of experience.