We don't really need any formal theory here. A little intuition is all it takes to see that the uncertainty of a project's completion time is a function of the number (and uncertainty) of all of the project's sub-projects.
Therefore, typical projects aren't just forecasts of the future, they're a series of nested forecasts of the future. As each sub-project's actual completion time comes in over its estimated completion time, the total project's completion time skews ever farther to the right.
When confronting our behavioral patterns in this way, it would seem like this should an easy problem to solve: we need to be more realistic with time estimates.
It's not that easy.
We are finally getting smart enough to know we're kinda dumb
Unfortunately, knowing that we should be better at estimating time and actually doing it are vastly different neurological notions. When it comes to accurately planning projects, we are swimming upstream against powerful psychological currents. Our brains weren't designed to map the future accurately beyond more than a few time steps.
These behavioral biases have been well documented under the so-called planning fallacy. Our minds evolved to have an overconfidence bias and hyperbolically discount the benefits and costs of far-off events. We're able to do a decent job of forecasting our immediate future, then we implicitly hope that only roses grow beyond our field of view. We block past experience from our mind, and repeat the same mistakes over and over and over again.
To be clear, I'm not talking about stupid people. Just people. These are fundamental features of the human mind. We are poorly adapted to do the kind of project planning that modern work requires. Our priorities dramatically and inconsistently change with time, and this is exacerbated by a modern world where all of our basic needs are met, leaving us to create and manage extremely abstract priorities to deliver products and services that are mostly exchanged in our minds.
Simply put, projects are complicated. Far more complicated than we give them credit for. We can't expedite human evolution, so let's bring projects back to us. Let's dumb them down for the emotionally handicapped creatures that we are.
One idea that makes sense to me: let's look at the characteristics of successfully completed projects and see if we can recreate those conditions for other projects. It's easier than it sounds.
First, care. Then, schedule.
Once upon a time, Merlin Mann said "First, care. . . Because, in the absence of caring, you'll never focus on anything more than your lack of focus."
No one can objectively argue against this caring principle. The catch: caring is entirely made of human emotion. At one extreme, caring is the arousal induced by productivity porn—you know it when you feel it, but you can't measure it. At least not like time. Caring is a very different substance than time, which in many ways is the antithesis of emotion. But both time and caring must be present to complete a project—any project.