Navigating Anchor Relevance Skillfully: Expertise Reduces Susceptibility to Anchoring Effects

50 years ago Tversky and Kahneman (1974) described anchoring as the phenomenon whereby an irrelevant numerical value influences a subsequent numerical judgment. Although expertise strongly influences the accuracy of judgments, its role in anchoring is still unclear with findings of reduced, similar, and stronger anchoring in experts compared to novices. Moreover, three prominent theories of anchoring, i.e., the Insufficient Adjustment Model, the Selective Accessibility Model, and the Scale Distortion Theory, make different predictions regarding the influence of expertise on anchoring. To address this inconsistency and to test these theories of anchoring against each other, we manipulate individuals' expertise prior to a perceptual estimation task. Additionally, we manipulate anchor relevance and anchor extremity. In two preregistered experiments, we find that experts do indeed show less anchoring compared to novices, and that more extreme anchors lead to stronger anchoring effects. However, we do not find an effect of anchor relevance in either experiment. These results add to the growing body of literature showing that expertise reduces anchoring effects. Morevoer, although no anchoring theory is clearly supported in the experiments, the results are mostly consistent with the Insufficient Adjustment Model assuming ranges of plausible values and the Scale Distortion Theory. Our findings highlight the importance of expertise in judgments in general and anchoring in particular. Thus, theories of anchoring should take expertise into account as a strong inhibitor of anchoring effects.