Everyday Experiences… Explained by Psychology

Half an Hour… and Two Hours Pass

You tell yourself, "This report will take half an hour."

You start working. Half an hour passes, then an hour, and after two hours you discover that you are still editing, reviewing, and searching for a missing piece of information.

The next day, you look at another task with much the same confidence: "This one is simple… it won't take long."

And the pattern repeats.

You may be organized and know your work well, yet still misjudge how long it will take. One reason lies in the way we imagine the future.

When we estimate the duration of a task we have not yet started, we may construct an orderly version of it in our minds: we will start immediately, stay focused, have the information ready, and need no time to redo anything.

We calculate the time as though the task will proceed without any obstacles.

But while we work, a call comes in, a message needs a reply, a file will not open, information turns out to be missing, and a paragraph needs several revisions. A small decision may consume time we never included in our estimate.

These details seem peripheral when we look at the task from a distance. Together, however, they become a substantial part of the time it requires.

Daniel Kahneman and Amos Tversky described this tendency as the planning fallacy: estimating the time needed to complete a task too optimistically, even when similar experiences suggest it usually takes longer. This is associated with focusing on the details of the current plan more than on the outcomes of previous tasks. Kahneman and Tversky, Intuitive Prediction.

You may have done similar work ten times before, yet treat the next attempt as an exception:

"This time is different."

You will start earlier, there will be no interruptions, and things will be simpler. Meanwhile, you find a specific explanation for the previous delay: a family situation, a technical problem, or information that arrived late.

Those explanations may be accurate. But the recurrence of different disruptions deserves a place in your estimate too. Yesterday's problem disappearing does not mean tomorrow will be free of problems.

In a study published by Roger Buehler and his colleagues in 1994, students estimated that completing their theses would take about 34 days on average. Actual completion took about 56 days among those for whom completion data were available. This finding concerns a particular sample and task, but illustrates how wide the gap between expectation and completion can become. Original study.

A familiar everyday example is saying, "The place is twenty minutes away."

That may be a reasonable estimate of the driving time shown by a navigation app, including its estimate of traffic conditions. But your arrival time also depends on getting ready, leaving the house, waiting for the elevator, reaching the car, finding parking, and walking to your destination.

Twenty minutes describes part of the journey, while you need an estimate for the whole journey.

This illustrates what we may leave out of our calculations: we see the report but overlook the revisions it will need. We see the driving time but overlook the minutes spent looking for parking. We see the steps of the task but overlook the life that happens between those steps.

The same pattern may appear when packing a suitcase, preparing a presentation, writing a paper, or organizing a move. We know what needs to be done, but knowing the steps is not enough to estimate how long they will take.

Before saying, "It will be finished in an hour," look back at a similar task and ask:

"How long did it actually take me on previous occasions?"

Then consider what has changed this time. Are the materials ready? Is there less work? Do you need to wait for someone else's response? Base your estimate on these specific differences.

In one experiment in Buehler and colleagues' research, optimistic bias disappeared in the group instructed to connect their past experiences with their current prediction. This supports using past experience directly when planning, while taking differences in the task and circumstances into account. Buehler and colleagues, 1994.

You can try this with recurring tasks: record the time you expected, the time you actually needed, and what accounted for the difference. After several attempts, you will have a reference that more closely reflects your real working day.

If reviewing a report is a recurring part of the work, it deserves time in the plan. If you always wait for information from a colleague, that waiting is part of the completion time. When circumstances vary, a range may be more useful than a precise figure that suggests certainty we do not have.

Sometimes our past record is more reliable than our present feeling.

When you plan for half an hour of work, remember that it will take place within a whole day, with everything that day brings.