[bloorp]

One big factor that I don't THINK the article touches on is how we are using 'space' metaphors (speed and distance) for our work that's very 'time' based (working productivity and duration). And I think when we estimate, we try to estimate distance/duration but we forget that we're really trying to estimate our speed/productivity.

Where that gets painful is, say you estimate you can get something done in two days. In reality, you're twice as fast (there's that speed metaphor), so you actually get it done in one day. Yay, you saved a day! Now assume you're twice as slow as your two day estimate. Boo, you spent TWO days longer. So in terms of duration, getting it incorrect in the painful direction seems like a bigger mistake.

I don't think this is the same phenomenon as the author's mean vs. median dilemma. I'll bet both the mean vs. median and the productivity vs. duration dilemmas are real factors though.