Consider the opposite

Actively argue the case against your first conclusion before accepting it.

Why it works

Confirmation bias makes System 1 retrieve only evidence that fits the conclusion it already reached. Deliberately asking "what would make this wrong?" forces retrieval of disconfirming evidence, counteracting the one-sided search that produces overconfidence.

How to do it

1. State your conclusion, then ask: "Suppose this is wrong — why?"
2. List concrete reasons and evidence that point the other way.
3. Only then re-weigh; the goal is calibration, not flipping for its own sake.

Evidence

"Consider the opposite" is one of the better-supported debiasing techniques, shown in experiments to reduce overconfidence and hindsight and confirmation effects. Koriat, Lichtenstein, and Fischhoff (1980) pin down why it works: overconfidence tracks a one-sided search for reasons, and deliberately generating reasons the judgment could be wrong is what recalibrates the confidence. (rct)

It reduces but does not eliminate bias, and it costs effort — people drop it under time pressure.

Sources

• Lord, Lepper & Preston (1984), considering the opposite reduces biased assimilation, J. Personality & Social Psychology
• Lord, C. G., Lepper, M. R., & Preston, E. (1984). Considering the opposite: A corrective strategy for social judgment. Journal of Personality and Social Psychology, 47(6), 1231–1243.
• Koriat, A., Lichtenstein, S., & Fischhoff, B. (1980). Reasons for confidence. Journal of Experimental Psychology: Human Learning and Memory, 6(2), 107–118.

Common mistake

Generating a token counter-argument you never believed, then dismissing it. The exercise only works if you genuinely try to build the opposing case.