Scope Creep and the Planning Fallacy

Google "scope creep" and you get over 10.1 million hits. Mission creep gets 15.6 million. Feature creep also gets over 20.2 million. That's pretty good for a technical concept, even if it isn't quite "miley" territory (222 million). The concept is known widely enough that anyone with project involvement has probably had first-hand experience with scope creep.

If we know so much about scope creep, why haven't we eliminated it? One simple possible answer: Whatever techniques we're using probably aren't working. Maybe the explanation is that we're psychologically challenged — that is, we, as humans, have a limited ability to detect scope creep, or to acknowledge that it's happening. If that's the case, a reasonable place to search for mechanisms to explain its prevalence is the growing body of knowledge about cognitive biases.

A cognitive bias is the tendency to make systematic errors of judgment based on thought-related factors rather than evidence. For example, a bias known as self-serving bias causes us to tend to attribute our successes to our own capabilities, and our failures to situational disorder.

Cognitive biases offer an enticing possible explanation for the prevalence of scope creep despite our awareness of it, because "erroneous intuitions resemble visual illusions in an important respect: the error remains compelling even when one is fully aware of its nature." [Kahneman & Tversky 1977] [Kahneman & Tversky 1979] Let's consider one example of how a cognitive bias can make scope creep more likely.

In their 1977 report, Kahneman and Tversky identify one particular cognitive bias, the planning fallacy, which afflicts planners. They The planning fallacy can lead to
scope creep because underestimates
of cost and schedule can lead
decision makers to feel that
they have time and resources
that don't actually existdiscuss two types of information used by planners. Singular information is specific to the case at hand; distributional information is drawn from similar past efforts. The planning fallacy is the tendency of planners to pay too little attention to distributional evidence and too much to singular evidence, even when the singular evidence is scanty or questionable. Failing to harvest lessons from the distributional evidence, which is inherently more diverse than singular evidence, the planners tend to underestimate cost and schedule.

But because the planning fallacy leads to underestimates of cost and schedule, it can also lead to scope creep. Underestimates can lead decision makers to feel that they have time and resources that don't actually exist: "If we can get the job done so easily, it won't hurt to append this piece or that."

Accuracy in cost and schedule estimates thus deters scope creep. We can enhance the accuracy of estimates by basing them not on singular data alone, but instead on historical data regarding organizational performance for efforts of similar kind and scale. And we can require planners who elect not to exploit distributional evidence in developing their estimates to explain why they made that choice.

In coming issues we'll examine other cognitive biases that can contribute to scope creep.   Next issue in this series   Top    Next Issue

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More about scope creep

Some Causes of Scope Creep  [September 4, 2002]

When we suddenly realize that our project's scope has expanded far beyond its initial boundaries — when we have that how-did-we-ever-get-here feeling — we're experiencing the downside of scope creep. Preventing scope creep starts with understanding how it happens.

Scopemonging: When Scope Creep Is Intentional  [August 22, 2007]

Scope creep is the tendency of some projects to expand their goals. Usually, we think of scope creep as an unintended consequence of a series of well-intentioned choices. But sometimes, it's much more than that.

More Indicators of Scopemonging  [August 29, 2007]

Scope creep — the tendency of some projects to expand their goals — is usually an unintended consequence of well-intentioned choices. But sometimes, it's part of a hidden agenda that some use to overcome budgetary and political obstacles.

The Perils of Political Praise  [May 19, 2010]

Political Praise is any public statement, praising (most often) an individual, and including a characterization of the individual or the individual's deeds, and which spins or distorts in such a way that it advances the praiser's own political agenda, possibly at the expense of the one praised.

The Deck Chairs of the Titanic: Task Duration  [June 22, 2011]

Much of what we call work is as futile and irrelevant as rearranging the deck chairs of the Titanic. We continue our exploration of futile and irrelevant work, this time emphasizing behaviors that extend task duration.

The Deck Chairs of the Titanic: Strategy  [June 29, 2011]

Much of what we call work is about as effective and relevant as rearranging the deck chairs of the Titanic. We continue our exploration of futile and irrelevant work, this time emphasizing behaviors related to strategy.

Ground Level Sources of Scope Creep  [July 18, 2012]

We usually think of scope creep as having been induced by managerial decisions. And most often, it probably is. But most project team members — and others as well — can contribute to the problem.

Scope Creep, Hot Hands, and the Illusion of Control  [February 26, 2014]

Despite our awareness of scope creep's dangerous effects on projects and other efforts, we seem unable to prevent it. Two cognitive biases — the "hot hand fallacy" and "the illusion of control" — might provide explanations.

Scope Creep and Confirmation Bias  [March 12, 2014]

As we've seen, some cognitive biases can contribute to the incidence of scope creep in projects and other efforts. Confirmation bias, which causes us to prefer evidence that bolsters our preconceptions, is one of these.

On Planning in Plan-Hostile Environments: I  [April 23, 2025]

In most organizations, most of the time, the plans we make run into little obstacles. When that happens, we find workarounds. We adapt. We flex. We innovate. But there are times when whatever fix we try, in whatever way we replan, we just can't make it work. We're working in a plan-hostile environment.

Footnotes

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