Kahneman and Tversky also believed that people used this heuristic to understand and predict other's behavior in certain circumstances and to answer questions involving counterfactual propositions. People, they believe, do this by mentally undoing events that have occurred and then running mental simulations of the events with the corresponding input values of the altered model. For example, a study was proposed that provided a group of participants with a situation describing two men who were delayed by half an hour in a traffic jam on the way to the airport. Both men were delayed enough that they both missed flights on which they were booked, one of them by half an hour and the second by only five minutes (because his flight had been delayed for 25 minutes). The results showed that a greater number of participants thought that the second man would be more upset than the first man.