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It’s Easy to Underestimate How Much Time You Need to Do Things

·342 words·2 mins
Psyched for the Weekend

“Oh yeah,” Past Me said. “This is a great plan. I’ll have plenty of time to get it all done.”


Of course _she’d _say that. She never has to actually _do _anything she signs me up for.

What a jerk, Past Me.

Typically, I’ll find myself cursing her, her optimism. As I’m slogging through some epic task that she thought I’d be able to get hammered out in no time at all. Having to sacrifice my other responsibilities, sleep, my sanity, in order to come anywhere near to meeting the deadline she set. The one that had seemed like a breeze to her.

Planning Fallacy

This tendency for a person to underestimate the amount of time it’ll take them to complete a task is called “planning fallacy.”

Planning fallacy was first named in 1979 by Daniel Kahneman and Amos Tversky and is intimately related to another cognitive distortion called optimism bias. People who commit the planning fallacy become overly optimistic about how long it’ll take them to complete a project and will therefore underestimate the amount of time needed to finish it.

Interestingly, this phenomenon only seems to affect the person who is doing the task. According to later studies, outside observers instead will typically exhibit a pessimistic view of how long it will take others to complete a task and will instead _overestimate _how long it’ll take others to complete it.

All of this leads a person to wonder: If you want to figure out how long something will _actually _take, should you take your own estimate and ask a friend for theirs and average them?


This post is part of an ongoing Poly Land feature called Psyched for the Weekend, in which I geek out with brief takes about some of my favorite psychological studies and concepts. For the entire series, please see this link.


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