A Nobel Prize-winning psychologist explains why we’re always wrong about how long tasks take

Why we’re wired to miss our own deadlines.
Why we’re wired to miss our own deadlines.
Image: AP Photo/Seth Wenig
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In an interview with The Cut on Tuesdays podcast, Serial podcast co-creator Sarah Koenig revealed the Achilles’ heel of her otherwise admirable journalism career: time management.

“I’m continually shocked at my wildly inaccurate estimations of how long something takes to do,” she told host Molly Fischer. Koenig continued:

I’ve been doing this a long time—I’m almost 50—and I’m still like, “Oh yeah, it’ll take a day.” I work super closely with my partner and Serial co-creator Julie Snyder, but I make my own schedule like, “Okay, these are the beats of the story I need to get done. Monday…” And then Thursday morning I’m still so behind, and I’m like, ‘What’s wrong with me?’ This happens every time.

If this sounds uncomfortably familiar, you are not alone. The human tendency to underestimate the amount of time a project will take to complete is known as the planning fallacy. It’s among the cognitive quirks psychologists Amos Tversky and Daniel Kahneman identified in their influential 1979 paper on the blind spots and biases that thwart decision making.

Examples of the planning fallacy in action can be as grand as a massive public works program like Boston’s “Big Dig” (a highway construction project completed nine years late and $22 billion over budget) or as small as the seemingly quick errand that somehow takes a day.

Whatever the outcome, the planning fallacy stems from two primary mistakes, Kahneman wrote in his memoir Thinking, Fast and Slow. A fallacious plan assumes both best-case conditions (no storms or political crises will disrupt construction; you will not get a cold or a last-minute request that derails your plans) and fails to consider the data presented by similar cases (yes, the last three assignments took me a week—but this time I know I can get it done in three days).

Unrealistic deadlines abound in situations where the costs of overruns are borne by someone other than the person presenting the plan. But it happens even in situations where failure is very much the planner’s problem. We fall into this trap again and again because success is so much easier to imagine than failure, Kahneman writes. There is often only one correct outcome we hope to achieve, yet countless ways for the plan to go haywire.

The check against the planning fallacy is to look beyond yourself. The most accurate benchmark for a task’s time is not your personal evaluation of your ability to complete the task this time, but the time it has taken others to deliver similar outcomes before. When pitching a glittering new project, the most realistic estimates of delivery time will come from checking with colleagues or reviewing data on how long comparable projects took them—and adjusting your over-optimistic projections accordingly.

It isn’t easy. “The intriguing aspect of this phenomenon is the ability of people to hold two seemingly contradictory beliefs: Although aware that most of their previous predictions were overly optimistic, they believe that their current forecasts are realistic,” social psychologist Roger Buehler wrote in a 1994 paper on the planning fallacy. “It seems that people can know the past and yet still be doomed to repeat it.”