Sophistry
No. 09 Cognitive bias

Dunning-Kruger Effect

The less someone knows about a topic, the worse they tend to be at judging their own knowledge of it.

A curve of confidence plotted against knowledge, peaking where knowledge is lowest, against a diagonal where the two would match. a b c
FIG. 9aa, peak confidence at almost no knowledge. b, the drop as real knowledge arrives. c, where confidence and knowledge would match. The hatched wedge is the overestimate.

Illustrative example

Someone who read one article on nutrition confidently correcting a dietitian in the comments.

Judging how much you know about a subject is itself a skill, and it’s one of the first skills that’s missing when someone knows very little about that subject.

This is why a small amount of knowledge can produce a lot of confidence: the gaps in understanding are exactly what’s needed to see how large the remaining gaps are.

Confidence isn’t evidence of competence. Ask how deep someone’s actual experience with a topic goes, not just how sure they sound.

The figure in motion

FIG. 9b

FIG. 9ba, Maya reads a single article, captioned "1 article read". b, she corrects Dr. Owens over lunch, captioned "Dr. Owens, 15 years as a dietitian". c, a rising confidence line is drawn over the scene against a flat line of actual knowledge. d, Maya's certainty falters. Narrated; captions carry the narration and the on-screen text.

Seen in the wild

Real, sourced instances of this technique in actual public debate.

Examples are chosen for how clearly they show the technique, not for who said it.

Dominic Raab

Leans right

Secretary of State for Exiting the European Union

“I hadn't quite understood the full extent of this, but if you look at the UK and look at how we trade in goods, we are particularly reliant on the Dover-Calais crossing.”

November 7, 2018 (Brexit and tech industry event, London)Irish Times report quoting the remarks, matching wording reported by the BBC and HuffPost UK (opens on the source site)

Watchthe remark, on video (opens on the site hosting the footage)
Context
Said at a Brexit and technology event three months into his tenure as the cabinet minister responsible for negotiating the UK exit from the EU, and after he had spent years publicly arguing the case for leaving. Dover-Calais was already the busiest route for goods entering and leaving the country.
Reading
The admission is the interesting part, and to his credit he made it in public. What it reveals is the gap the effect describes: the confidence he had already expressed about how leaving would work was formed without knowing a fact this basic, which means his earlier sense of how well he understood the problem was not tracking how well he actually understood it. Knowing enough to notice what you are missing is a later stage than it feels.

Know a good example?

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