# Predicting how long a task will take

As a software engineer I have always struggled with predicting how long a project would take by underestimating and I have noticed that all of my colleagues have the same problem. In this video at 3:32 Luke Jones labels this problem The familiar road phenomena where people underestimate how long a task will take when they are familiar with the task.

• What studies have been conducted on the familiar road phenomena?
• Why do humans do this and what is the evolutionary advantage?
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More as a comment: Evidence Based Scheduling - Joel on Software and search for "unrealistic optimism" or optimism bias plus many delays are due to "unpredictable" problems, so you can't just include them in a schedule. – Piotr Migdal Feb 5 '13 at 17:08
The book Software Estimation: Demystifying the Black Art has a good example that shows that most people's assumption of "90% confidence" is drastically below 90%.. it's in fact closer to 20% confidence. The more familiar you know something, the narrower your estimate will be, and the more likely you'll miss your estimate. – Muz Feb 28 '13 at 10:08

If someone is familiar with repeating a task, it becomes a habit. Routines within a habit take less brain power. With less conscious effort needed to do it, someone would most likely underestimate or gloss over what the task consists of.

This is just one possible interpretation; there might be other reasons as well.

The evolutionary advantage would be that we need less mental resources to deal with things we are familiar with. We would say, struggle to learn to peel a potato at first, but after a few dozen/hundred times, we do it effortlessly. The brain will try to optimize these things into a habit loop to conserve resources needed to do things. Without habits, we would spend too much time on 'simple' things like recognizing a person's facial features.

Source: Duhigg, Charles. The Power of Habit: Why We Do What We Do in Life and Business. Random House, 2012.

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