Set a deadline for tasks without an external deadline
When someone else sets the deadline, 80.6% of students finish before it. Only 38.7% finish within the time they themselves expected. When the work gets done almost follows the deadline set by others, and has little to do with their own estimate. For a task with no deadline, you can use this approach to set one yourself and commit to it.
No cost involved. The hard part is actually sticking to th…
For students with an external deadline, 80.6% complete their work before it. Meanwhile, only 38.7% finish with…
No cost involved. The hard part is actually sticking to the deadline you set. If you ignore it when the day arrives, it’s as if you never set it at all.
For students with an external deadline, 80.6% complete their work before it. Meanwhile, only 38.7% finish within their own estimated timeframe. The actual completion time closely aligns with the external deadline, with a correlation coefficient of r = 0.82 — the closer this number is to 1, the tighter the alignment. There is only a very weak link between completion time and students’ own estimates.
Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the "planning fallacy": Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366–381. https://doi.org/10.1037/0022-3514.67.3.366；Ariely, D., & Wertenbroch, K. (2002). Procrastination, deadlines, and performance: Self-control by precommitment. Psychological Science, 13(3), 219–224. https://doi.org/10.1111/1467-9280.00441（2026 年已撤稿，撤稿声明：Retraction: Procrastination, Deadlines, and Performance: Self-Control by Precommitment. Psychological Science. https://doi.org/10.1177/09567976261488042）；Hyndman, K., & Bisin, A. (2026). Replication of "Procrastination, Deadlines, and Performance: Self-Control by Precommitment". Psychological Science：「changes in the deadlines had a negligible effect on the three performance metrics and several survey metrics used in the original study」. https://doi.org/10.1177/09567976261460772
Open source linkTell other people the date you set, and it moves closer to the kind someone else sets. What the research checked is that deadlines set by other people work. Self-set versions, such as time boxes and Pomodoro timers, are an extrapolation here. One experiment did directly test self-imposed deadlines: Ariely and Wertenbroch’s 2002 paper. The journal retracted it in 2026. A replication published that same year found that how deadlines were set had only small effects on performance.