Planning fallacy

You agree to send a draft by Friday. It is Monday, and the draft looks small. By Thursday night you have not started the hard part, and the hard part was always going to take two days.

When it runs over, the reason seems to be bad luck. A meeting moved. Someone needed you. Something came up. Next time you plan as if nothing will come up, again.

Every overrun had a reason. Every next plan forgot all of them.

The term comes from psychology research. The archive's Myth File on how long your own tasks take reads the paper that put the phrase in its title, in abstract. That paper reports several studies, with tasks from school and from daily life.

People's guesses for their own tasks were too hopeful. While guessing, they thought mostly about how the task would go this time. They leaned little on how past tasks went. They also explained away past overruns, blaming outside causes tied to that one time.

Guessing for someone else went the other way. Observers gave other people too much time, and used past tasks more. When people were asked to link past tasks to their guess, the too-hopeful guessing went away. The abstract gives no count of people and no size for the error, so this page does not either.

The planning fallacy is a finding about guesses. Everyone makes it. It is not a diagnosis and it is not one of the nine patterns. That paper did not test this method.

For most people a short guess costs a late night now and then. For some, it is one link in a longer chain. The Perfectionism Trap is the pattern of not finishing what is not perfect. You may know it as the late night that ends in a rushed finish, then a fresh plan that is just as short. The short guess keeps the plan perfect on paper, and a plan that is perfect on paper never has to meet the real work.

The research fix is simple: look at past tasks before you guess. If you know that fix and still write the short number, the guess is not the whole story. Something moves in the body as you write it.

Watch the moment you are about to write down a time or agree to a date. Feel what your body does. For some people there is a small lift, a sense of relief, as the short number lands. For others the chest tightens at the thought of a longer one. That is the body signal, the first thing you feel in your body as the pattern starts. Name it: there is the short guess.

Then say one short sentence out loud. A whisper counts.

Then take the different action instead of the usual response. The usual response is to write the hopeful number. The different action is to look up how long the last one like it took, and use that number. If you have no record, ask someone who watched you do it.

Count that as one rep, which means one repetition of checking before you guess. Keep it small. One task this week is enough.