Does anchoring cause overconfidence only in experts?


The anchoring-and-adjustment heuristic (Tversky & Kahneman, 1974) predicts elicitation of an initial estimate will prompt subsequent minimum and maximum estimates to lie close to the initial estimate, resulting in narrow ranges and overconfidence. Evidence for this, however, is mixed; while Heywood-Smith, Welsh & Begg (2008) observed narrower subsequent ranges, Block and Harper (1991) report ranges became wider. One suggestion has been that this reflects a difference between expert and novice reactions to elicitation tasks. The present study investigated whether the interplay between expertise and number preferences leads to the paradoxical effects of an initial estimate. Participants with high expertise make precise estimates whereas participants with less expertise prefer rounded numbers, which could, potentially, reduce the impact of anchors. We confirm that expertise affects the precision of estimates and observe results indicative of the theorized effect – an interaction between expertise and elicitation method on range widths.

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