As with a lot of the research done on cognitive biases, we have psychologist Daniel Kahneman to thank for the first studies of the peak-end rule. In 1993, he and colleagues Barbara Fredrickson, Charles Schreiber, and Donald Redelmeier published one study in Psychological Science intriguingly titled "When More Pain Is Preferred To Less."

For the study, they asked participants to dunk one hand in water chilled to 14ºC (57ºF) for 60 seconds. That's a temperature deemed "very dangerous" for swimming by the National Center for Cold Water Safety, which is apparently a thing. Next, they asked the same participants to do the same thing with the other hand, except they kept their hand in the water for an additional 30 seconds while, unbeknownst to the participants, the experimenters gradually increased the water temperature to 15ºC (59ºF) ("still painful but distinctly less so," according to the study). Finally, they asked participants which trial they'd like to repeat for the third experiment. A majority chose the second trial, even though it technically put them through more pain than the first trial. The big difference was that they were in noticeably less pain near the end.

Kahneman and his colleagues tested and retested this hypothesis with film clips, colonoscopies, even watching other people's discomfort. Time and again they found that when asked to judge an experience in retrospect, people's ratings could be predicted by a combination of the overall discomfort level and the discomfort level at the end of the experience. It didn't matter how long the experience lasted; people mostly remembered how uncomfortable it was near the end.

A more recent study found this to be true with pleasant objects, as well: people generally judge getting one good thing for free (a highly rated DVD or a chocolate bar, in these cases) to be better than one good thing packaged with a slightly less good thing (a DVD with a mediocre rating or a piece of bubble gum).

Knowing your own biases can help you "hack" your future experiences. The next time you want to remember something fondly, says Susan Krauss Whitbourne, Ph.D., keep these three tips in mind: first, when engaged in something seemingly negative, keep your mind focused on your overall goals for that experience. For example, while getting a filling, think about how good it'll feel to eat without pain. Second, don't let minor discomforts ruin good experiences. If the waiter forgets to fill your water during a romantic anniversary dinner, let it slide and focus instead on your beloved.

Finally, try to make sure your experiences end on a high note. Is staying until the concert's encore worth the misery of being stuck in the parking lot for hours? If not, you might want to skip the final song and make the concert one to remember fondly.