04-008 · EVIDENCE B · LOW-RISK READING
Set a deadline for tasks without an external deadline
给没有外部截止的事自己定一个日期
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.
When there is an external deadline, 80.6% of students manage to finish their work before it. But only 38.7% finish within their own estimated timeframe. The actual completion time is almost entirely determined by the external deadline, with little connection to their own estimates. That’s why it’s crucial to set your own deadline for tasks with no external deadline, and then follow through on it.
B
Move “Set a deadline for tasks without an external deadline” to Future Me's calendar
The excuse
There is no immediate alarm, so the sensible choice can wait for a less busy week.
What feels good now
Today I keep a few minutes, a bit of persistence and avoid interrupting my default routine.
What the source says
The source summarizes the return this way: “When there is an external deadline, 80.6% of students manage to finish their work before it. But only 38.7% finish within their own estimated timeframe. The actual completion time is almost entirely determined by the external deadline, with little connection to their own estimates. That’s why it’s crucial to set your own deadline for tasks with no external deadline, and then follow through on it.” Evidence grade B. The original states the population, caveats, and sources; this is not a personal forecast.
Open the original entry, check who the evidence applies to, then pick one small step that fits.
THE ENGLISH EDITION
Original recommendation and evidence
8. Set a deadline for tasks without an external deadline
Cost: 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.
In plain terms: When there is an external deadline, 80.6% of students manage to finish their work before it. But only 38.7% finish within their own estimated timeframe. The actual completion time is almost entirely determined by the external deadline, with little connection to their own estimates. That’s why it’s crucial to set your own deadline for tasks with no external deadline, and then follow through on it.
Benefit: 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.
Evidence grade: B
Sources: 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>
Notes: Telling others about the deadline you set for yourself makes it behave more like an external deadline. It’s worth noting that this research only proves external deadlines are effective. For self-set deadlines such as time-boxing or using Pomodoro timers, no direct studies have been conducted, so this conclusion is drawn by inference.
Read the complete Chinese source and notes
8. 给没有外部截止的事自己定一个日期
成本: 不花钱。难在定了就要认，到了那天不当回事就等于没定。
说人话: 有别人定的截止日期时，80.6% 的学生能在那之前做完。按自己预计的时间做完的，只有 38.7%。什么时候做完，几乎由截止日期决定，和自己估的关系不大。所以没有截止日期的事，自己给它定一个，并且认账。
收益: 有外部截止日期的学生，80.6% 在截止前完成。而在自己预计的时间内完成的，只有 38.7%。什么时候做完，几乎跟着截止日期走，相关系数 r = 0.82，这个数越接近 1 说明跟得越紧。和自己的预计只有很弱的关系。
证据等级: B
来源: 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>
备注: 把自己定的日期告诉别人，它就更接近别人定的那一种。要说明的是，研究验证的是别人定的截止日期管用。自己给自己定的那种，比如时间盒、番茄钟，没人直接测过，这里是照着推的。
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