Bias in memory predicts bias in estimation of future task duration.

Both anecdotal accounts and experimental evidence suggest that people underestimate how long it will take them to complete future tasks. A possible reason for this tendency is that people remember tasks as taking less time than they actually did, with these biased memories causing a corresponding bias in prediction. Two experiments were performed to determine whether or not a systematic bias in memory could explain a similar systematic bias in prediction. In support, it was found that (1) the tendency to underestimate future duration disappears when the task is novel, (2) there is similar bias in estimation of both past and future durations, and (3) variables that affect memory of duration, such as level of experience with the task and duration of delay before estimation, affect prediction of duration in the same way. It appears that, at least in part, people underestimate future event duration because they underestimate past event duration.