Making better decisions starts with understanding this: uncertainty can work a lot of mischief. - Annie Duke

Over the past forty years, researchers in well over a hundred subsequent studies have replicated and expanded on Thaler's initial work. The early demonstrations of the endowment effect in the lab were quite simple. In one of Jack Knetsch's early experiments, students signed up for the task of completing a questionnaire. Before filling it out, one group of participants received their payment in the form of a coffee mug. A second group received payment in the form of a big chocolate bar. (A third group was offered a choice between the two as a fresh decision with no prior ownership of either. This group split pretty evenly, favoring the mug 56%–44%.) Knetsch wanted to know whether ownership of the mug or the chocolate bar among the first two groups would change how the participants valued those items. To do that, after completing the questionnaire, he gave the participants in those groups a chance to switch their payment for the other item. In other words, the students with the mug could trade for the chocolate bar, and the students with the chocolate bar could trade for the mug. If there was no effect of ownership, you would expect that the first two groups, after trading when they preferred the other item, would end up with the same proportion of mugs and chocolate bars as those who came to the decision fresh. About half the participants in each group would trade, perhaps slightly more in the group that started with the chocolate bar and slightly fewer in the group starting with the mug. But that's not what Knetsch found. It turned out that endowment to an item, even for such a brief period of time, had quite a strong effect on how much value they attached to the items. Of those given the mug, 89% declined to trade it for the chocolate bar. Among those given the chocolate, 90% favored the chocolate and only 10% traded it for the mug.

The quality of the outcome casts a shadow over our ability to see the quality of the decision.

Over time, those world-class poker players taught me to understand what a bet really is: a decision about an uncertain future. The implications of treating decisions as bets made it possible for me to find learning opportunities in uncertain environments. Treating decisions as bets, I discovered, helped me avoid common decision traps, learn from results in a more rational way, and keep emotions out of the process as much as possible.