The Planning Fallacy: When the Hourglass is Half Full

Sometime in the middle of my freshman year, at the advice of a friend, I took a walk to the local dollar store and bought myself a calendar style daily planner. For years before then, I had relied entirely on a to-do list on my phone, adding and removing obligations as needed. It turned out to be a major improvement; I missed significantly fewer deadlines and it gave me the opportunity to get a general idea of what to expect from each coming week. Naturally, at the beginning of my sophomore year, I decided to take the next logical step and start scheduling hour-by-hour, at which point I promptly lost all the progress I had made. The problem was that, even when I added ‘buffer time’ to compensate, I still found myself underestimating the time I needed for anything that didn’t have a built in beginning and end, like classes and meetings.

Even this blog post was underestimated. A few days ago, I told myself I could definitely start and finish on Saturday night, leaving myself all of Sunday night to study for my exam at noon on Monday. How did things go so wrong? We might begin to answer that question by considering this explanation from a paper on intuitive prediction by Daniel Kahneman and Amos Tversky, which distinguishes between singular and distributional data. The former, according to the authors, is based on the various factors which characterize a scenario, while the latter is based on comparisons with other similar scenarios. In other words, as applied to homework, a singular approach might be based on the time needed to choose a topic, conduct my research, pull useful information from my sources, and so on. A distributional approach, by contrast, would draw on my prior experience in similar assignments (including the last two blog posts), as well as any information I happen to have about how long it takes my peers.

Kahneman and Tversky identify the over-reliance on internal models (singular data) as the primary component of what they called ‘the planning fallacy’. Even disregarding the complementary effects of wishful thinking, it seems that even experts tend to create unreasonable time estimates based on a preference for internal rationalizations. The article reasons that external (distributional) assessments tend to yield more accurate results because they account for the multitude of possible complications which would otherwise be unaccounted for on the basis of individual improbability.

A research paper from 1994 by Buehler, Griffin, and Ross built on this dichotomy. Their first two studies concerned the completion of an Honors Thesis project and either an academic or personal task, respectively. Earlier predictions were correlated with earlier completion times but, in all cases, participants took consistently longer than they had planned despite reporting high levels of confidence in their numbers and even when asked to give a pessimistic estimate. In fact, the best predictor available turned out to be the externally established deadline for a project’s completion, although time-to-deadline was shown to have minimal influence on estimation.

The third study in the same paper asked participants to reason aloud while making their predictions, showing that future plans are disproportionately favored over all other considerations, although this study failed to support the researchers’ hypothesis that those who favored past experiences would generate more accurate estimates. However, the subsequent study was able to improve guesses under the specific case in which subjects were not only asked to consider similar past experiences, but were also forced to describe how said experiences were relevant to the future they were planning for.

Perhaps most interesting was the fifth and final study, in which observers were brought in and asked to make their own independent estimates for other participants after being given necessary information about the person they were assessing and the parameters of the project. These social predictions were consistently more conservative, with a day and a half on average more time given for one-week deadlines and over four days greater for two-week deadlines when compared to the individual predictions of those actually performing the task. Observers, as predicted, were more likely to use impersonal distributional data and were thus more accurate, just as with the prior task in which subjects were manipulated to relate their plans to past actions.

So what can we do differently to improve planning in our own lives? First, it is important to consider the task at hand in relation to similar tasks from past experience, which requires overcoming the mental bias towards viewing past complications as relatively externally caused and unique. Try to find ways in which the upcoming situation is specifically similar to what you already know about yourself and others, which will help to decrease the effects of over-optimism. Perhaps an even more practical approach is to outsource the planning entirely and enlist your friends to help. Due to their external perspective, they are far more likely to make estimates which prioritize their general knowledge over your best intentions, which leads to more realistic expectations.

5 thoughts on “The Planning Fallacy: When the Hourglass is Half Full

  1. kourt21

    I am all too familiar with ‘planning fallacy’. I fell into another one writing comments on other people’s blog posts. I told myself I would try to write one once a week until this blog post was due, but that plan was left unaccomplished. Then I told myself that I would do them over the weekend and here I am just finally completing one. I just overestimate the time that I have and underestimate the time that it takes to complete an assignment. Often I don’t account for other things that could possibly get in the way of me completing a goal. I think other psychological things get in my way as well, like my anxiety. I also have difficulty in picking a subject for a blog post or coming up with final exam questions because I feel like my topics aren’t good enough.
    -kchiles

  2. ctodd

    I needed to read this! I often find myself leaving a lot less time to do things because I am overly optimistic about how much I can do in a short amount of time. I often find myself saying “well I did that one 8 page paper in a few hours that one time”, not acknowledging how different an 8 page paper is from a blog/exam/SPSS assignment/etc. I also don’t allow myself wiggle room in case things come up-because things do come up. I see it as a mental barrier that you have to slowly chip away at as you develop better study habits and shape a better work ethic. But this all takes time.

  3. sierrahorton

    Hi, I was immediately intrigued by your topic because I am the type of person that loves a schedule and a good old fashioned to-do list. Interestingly enough, I also keep an hour by hour schedule on my phone; however, it seems to work for me. But, I do understand what you were saying about often underestimating the amount of time it takes to complete certain tasks. As time has progressed, I do believe I have gotten better at knowing how long it takes me to complete certain assignments, but I still understand where you’re coming from and I am glad I continued reading your post. Nonetheless, I like that you started your post with a personal take on schedules and planning. I really enjoyed reading about the research you brought into your post and the way you summarized and discussed the ‘planning fallacy’. In your concluding thoughts, I like the tip of enlisting the help of your friends when planning. I agree that this outsourcing would give an excellent external perspective and set you up well when it comes to prioritizing. Their realistic point of view is exactly what we need when we are so easily driven by emotions and other things which often lead us astray.

  4. nboigegrain

    Not to brag, but planning is not one of my problems in life. I can count on one hand that I have missed an assignment or turned something in late since elementary school. I think the main reason behind my accomplishment is that school is truly the focus of my life. I literally base most of my decisions around my classes and workload. However, that is actually kind of really depressing, so unless you love school and work, I do not suggest trying to base your life around it. I only do it because that is what my parents’ expect of me and of my extreme Type A personality. However, what I do suggest is planning. What I find works for me is that I will plan my entire week out every Sunday. However, this is a rough plan. I make a more detailed plan at the beginning of every day, but I make sure this plan is very flexible. I make sure I schedule off twice as much time that I think is necessary for almost every task and I do not tell myself when to do each assignment. The reason I do it this way is that I am taking into account that things generally take me longer to complete than I think they should and I recognize that I am more productive during certain parts of the day. I also recognize that I cannot predict what mood I will be in for each hour and that not scheduling something for each hour allows me to do what seems most appealing to me at the time, which not only increases my productivity level but also makes it seem more fun, or at least manageable.

  5. mbeidleman

    This post is extremely relatable because I am obsessed with schedules and keeping to-do lists. I used to make hourly schedules like you but I had to stop because it ended up just stressing me out. I would think I could get a whole paper done in a couple hours when the research alone would take that long. I decided to just make a list of assignments that I should be able to get done in a day, and even then sometimes I am not able to complete everything because I underestimate the amount of time that I think it will take me to finish all of my work. I have never heard of the planning fallacy, but now that I have, it makes so much sense. Although I’m getting a better idea about how much time I realistically need to allow for each assignment, I’m glad that there are so many others that end up in the same boat as me when it comes to planning how much I can get done in a certain amount of time.

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