{This post is part of the Archive of Human Exploits}
I first learned of this bias from Y Combinator's Paul Graham, likely from his essay, "How to Get Startup Ideas," in which he writes:
When searching for ideas, look in areas where you have some expertise. If you're a database expert, don't build a chat app for teenagers (unless you're also a teenager). Maybe it's a good idea, but you can't trust your judgment about that, so ignore it. There have to be other ideas that involve databases, and whose quality you can judge. Do you find it hard to come up with good ideas involving databases? That's because your expertise raises your standards. Your ideas about chat apps are just as bad, but you're giving yourself a Dunning-Kruger pass in that domain.Once I knew what it meant, that phrase "Dunning-Kruger pass" stuck with me — although I tended to misremember it as Dunning-Kruger bridge. (More on this in a minute.)
Graham also mentions the bias in "How to Convince Investors":
To evaluate whether your startup is worth investing in, you have to be a domain expert. If you're not a domain expert, you can be as convinced as you like about your idea, and it will seem to investors no more than an instance of the Dunning-Kruger effect. Which in fact it will usually be. And investors can tell fairly quickly whether you're a domain expert by how well you answer their questions. Know everything about your market.Here's a succinct explanation of the effect from The Decision Lab:
The Dunning-Kruger effect is a cognitive bias in which individuals are prone to assess their cognitive ability as greater than it truly is. Most simply, individuals who are the least competent at a task often incorrectly rate themselves as high-performing even when they lack particular knowledge or expertise.(Warning: The science part of the above finding is shaky. "Dunning-Kruger effects reported in the literature are mostly the result of statistical artefacts," argues social psychologist Lee Jussim.)
The Dunning-Kruger effect is related to the cognitive bias of illusory superiority and comes from the inability of people to recognize their lack of knowledge or ability. In turn, these individuals will lack the ability to recognize their own mistakes and errors, making them exceptionally confident and biased self-evaluators. They are also unable to fairly judge other people’s performance.
This bias was first described by social psychologists David Dunning and Justin Kruger in 1999. Dunning and Kruger found the bias by testing students in the areas of humor, grammar, and logic. They compared each individual student’s test results with the same student’s estimate of how well they scored. The results were that those who scored the lowest vastly overestimated their scores, while those who did best slightly underestimated their performance. It is illustrated in the graph below which shows those who have almost zero knowledge on a topic display low confidence, but those with a minimum level of competence vastly overestimate their abilities. As the level of knowledge increases, those who are more competent are more aware of the gaps in their knowledge and display lower confidence. On the far end of the spectrum are experts in a particular field who display a high degree of confidence.
My sense of this bias is as follows. Have you ever been offended when someone argues with you about your area of expertise even though they really don't know the first thing about it? You want to scream at them: "You couldn't [do even a simple version of this thing] if your life depended on it!" And yet they have the confidence to tell you what you should be doing, as if it's easy. They might even have the temerity to argue with you about it! How?! Well, that's Dunning-Kruger effect in action.
The interesting thing about it is the conditions necessary. In my experience, the effect is most common in people who have an unquestionable area of expertise themselves. It's just not your area, and it may not even be close. I've debated advertising techniques with a top-tier personal trainer, and what it takes to write well with several first-rate entrepreneur bosses. The trainer didn't know the first thing about advertising, and I've never had a boss who knew how to write well. So how do they get from warranted confidence to unwarranted confidence? From acceptable superiority to illusory superiority?
This may be where the idea of a Dunning-Kruger "bridge" stuck in my mind because I visualize it as building a bridge between concepts (or "domains," as Graham put it). We mistakenly assume that because the bridge starts with one end on solid ground, it ends with the other end on solid ground.
It doesn't, which is why it crumbles.
Related: An Ignorant Mind is Filled with Clutter
