In 1994, Roger Buehler and two colleagues phoned a group of psychology students who were finishing their honors theses. They asked each student to predict the day they would hand it in. They guessed five weeks on average. Then they asked a second question, what if everything went wrong? Allowing for disaster they guessed seven. In reality, it took them eight.[1]
They kept studying this line of thinking, eventually asking students for dates they were 50%, 75% and 99% certain they'd finish the project. Despite the new approach, less than half of them finished by the date they were 99% certain they'd be done.[2]
Daniel Kahneman and Amos Tversky named it in 1979.[3] The planning fallacy. It's a common hallmark of human planning, studied in software engineering, public planning, personal projects and elsewhere.[4] Buehler's work fifteen years later was built on it.
Unfortunately, even if you're aware of this problem, you're still susceptible to it. They studied if knowing their plans were often optimistic led to a change in the plans, but they still came in underestimating the time it would take.[2]
The gap between intention and behavior
When studying what happens when humans predict their own future behavior, the same problem occurs. A 2023 meta-analysis, covering 25 independent samples from 22 articles with a combined pool of nearly 30,000 people, found that of the people who intended to exercise, 52.4% did so, and 47.6% did not. The odds that someone turns their intentions into behavior is pretty much a coin flip.[5]
What about if a person wants it more, are they more likely to achieve their goals? Another meta-analysis was run, covering 47 experiments, where the scientists hyped up their subjects to see whether increased motivation led to more of the desired behavior. They ran motivational seminars, presented persuasive arguments and employed other tactics to help participants care more about specific goals.
These interventions worked, in the sense that people who got them did more than people who didn't. They just worked unevenly. Across these studies, while the interventions produced a small increase in what people did, they increased what they intended to do by twice as much.[6]
The effect doesn't disappear with recent experience either. Researchers paid college students to attend the campus gym for a month. At the end of that month they asked them how often they'd go once they stopped getting paid, then they tracked their gym card swipes. The students predicted they'd go between two times and four times as often as they actually went.[7]
Accounting for the planning fallacy
In every study above, the number people set is what turned their behavior into a failure. Regardless of what they did, the goal remained out of reach. The thesis writers finished. The gym-goers kept going. They only failed against a guess they made before they started.
Try Easier gives every habit two numbers. The ceiling is what you're aiming at on a normal week, the target any habit tracker asks you for. The difference is that you don't have to guess it yourself. The app asks how hard the habit feels and suggests a starting frequency, usually lower than the one you'd have picked. Override it if you disagree. Exceed it regularly and you can raise it.
The floor is once a week, and it never moves. Any week you show up is a week you've succeeded. Because a habit is something you're still doing a year later, regardless of whether you're doing it precisely as much as you thought you would.
Traditional habit trackers ask whether you hit the number. Try Easier asks whether you're still doing the thing.
