Kahneman and Klein (2009) trace overconfidence to subjective confidence tracking the internal consistency of the evidence rather than its quality

kahnemankleinoverconfidenceexpert-intuitionevidence-qualitycoherencecognitive-psychologyjudgment-under-uncertainty

Kahneman and Klein offer a causal account of why subjective confidence fails as a signal of validity: confidence is generated by how well the available evidence hangs together, not by how good that evidence is. "Subjective confidence is often determined by the internal consistency of the information on which a judgment is based, rather than by the quality of that information... As a result, evidence that is both redundant and flimsy tends to produce judgments that are held with too much confidence. These judgments will be presented too assertively to others and are likely to be believed more than they deserve to be."

This is the mechanism that makes low-validity environments specifically dangerous: they are exactly the settings where the available cues are weak, so any apparent coherence among them is spurious rather than earned — yet coherence, not quality, is what the confidence signal reads. It is the why beneath the paper's blunter finding that confidence does not discriminate valid from invalid intuition (claim-kahneman-klein-2009-skill-cannot-form-in-low-validity-confidence-does-not-signal-validity), and it sharpens the scope condition on claim-kahneman-klein-2009-intuition-reliable-only-in-high-validity-environments. The account is a close relative of Kahneman's later WYSIATI ("what you see is all there is") theme — judgment operates on the coherence of the evidence at hand and is blind to the evidence's provenance or sufficiency.