I think most people go through life without much cognitive dissonance. Human brains don't like it, and they do everything possible to smooth it over. That gets dangerous when the smoothing is used to cover up the single flaw most prevalent in human minds – the idea that we are above average.
You, me, the people you work with, your family, we all have certain areas of knowledge or certain skills that we think are very good, even when they aren't. We think we make honest assessments of ourselves because we are willing to admit the things we do poorly. We think the act of acknowledging a handful of shortcomings proves that we have an accurate view of ourselves. But that is irrelevant. It doesn't stop us from misjudging ourselves at the things we want to do well.
Studies have show that this bias is pervasive. Just look at some of the research:
Surveying drivers, Ole Svenson (1981) found that 80% of respondents rated themselves in the top 30% of all drivers. Asking college students about their popularity, Zuckerman and Jost (2001) showed that most students judged themselves to be "more popular than average".
In 1987, John Cannell completed a study that reported the statistically impossible finding that all states claimed average student test scores above the national norm.
One College Board survey asked 829,000 high school seniors to rate themselves in a number of ways. When asked to rate their own ability to "get along with others," a statistically insignificant number – less than one percent – rated themselves as below average. Furthermore, sixty percent rated themselves in the top ten percent, and one-fourth of respondents rated themselves in the top one percent.
If you don't want to read the research papers, just tune in to the early rounds of American Idol. Some people with horrible voices actually believe they can sing.
In business, this lack of self-knowledge leads to all sorts of problems. One such problem is know as Planning Fallacy, which is a tendency to underestimate task completion times. Lump all of these underestimations together, add a project manager that doesn't understand how the pieces of a project should flow together (which is often what you get when you promote technically competent people to management without any management training), and you have a certified, guaranteed, failure.
The natural question is – how can we overcome this? And no, the answer is not to pad the schedule every step of the way.
Think – This is a hard one, but don't just make up numbers
ways to avoid