Context: The role of expert judgement is essential in our quest to improve software project planning and execution. However, its accuracy is dependent on many factors, not least the avoidance of judgement biases, such as the anchoring bias, arising from being influenced by initial information, even when it's misleading or irrelevant. This strong effect is widely documented. Objective: We aimed to replicate this anchoring bias using professionals and, novel in a software engineering context, explore de-biasing interventions through increasing knowledge and awareness of judgement biases. Method: We ran two series of experiments in company settings with a total of 410 software developers. Some developers took part in a workshop to heighten their awareness of a range of cognitive biases, including anchoring. Later, the anchoring bias was induced by presenting low or high productivity values, followed by the participants' estimates of their own project productivity. Our hypothesis was that the workshop would lead to reduced bias, i.e., work as a de-biasing intervention. Results: The anchors had a large effect (robust Cohen's d = 1.19) in influencing estimates. This was substantially reduced in those participants who attended the workshop (robust Cohen's d = 0.72). The reduced bias related mainly to the high anchor. The de-biasing intervention also led to a threefold reduction in estimate variance. Conclusion: The impact of anchors upon judgement was substantial. Learning about judgement biases does appear capable of mitigating, although not removing, the anchoring bias. The positive effect of de-biasing through learning about biases suggests that it has value.
The cognitive basis of the anchoring bias is disputed and there are at least three different, partly overlapping, explanations: 1) Anchoring as communication (the attitude change theory), i.e., that it is natural for us to give weight to what other people communicate @cite_32 . 2) Anchors as a starting point (the anchoring and adjustment theory), i.e., that the anchor is the starting point and that the adjustment away from the anchor typically is insufficient @cite_31 . 3) Anchors as an activating experience (the selective accessibility theory), i.e., that the anchor activates experiences and that recently activated experience is more likely to be used in the subsequent judgement process @cite_1 . All explanations have supporting evidence and it is possible that they all contribute to the observed anchoring bias.
@cite_31 @cite_1 @cite_32
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This paper describes three heuristics, or mental operations, that are employed in judgment under uncertainty. (i) An assessment of representativeness or similarity, which is usually performed when people are asked to judge the probability that an object or event A belongs to a class or process B. (ii) An assessment of the availability of instances or scenarios, which is often employed when people are asked to assess the frequency of a class or the plausibility of a particular development. (iii) An adjustment from a starting point, which is usually employed in numerical prediction when a relevant value is available. These heuristics are highly economical and usually effective, but they lead to systematic and predictable errors. A better understanding of these heuristics and of the biases to which they lead could improve judgments and decisions in situations of uncertainty. Results of four studies support the notion that anchoring effects are mediated by mechanisms of hypothesis-consistent testing and semantic priming. According to the suggested Selective Accessibility Model, judges use a hypothesis-consistent test strategy to solve a comparative anchoring task. Applying this strategy selectively increases the accessibility of anchor-consistent knowledge which is then used to generate the subsequent absolute judgment. Studies 1 and 2 demonstrate that absolute estimates depend on the hypothesis implied in the comparative task, suggesting that a hypothesis-testing strategy is used to solve this task. Study 3 shows that limiting the amount of knowledge generated for the comparative task retards absolute judgments. This suggests that knowledge rendered easily accessible in the comparative judgment is used for the subsequent absolute judgment. Finally, Study 4 suggests that self-generation of knowledge contributes to the robustness of the effect, thus resolving the seeming inconsistency that anchoring effects are at the same time remarkably robust and mediated by typically fragile semantic priming mechanisms. Abstract Effects of extreme versus moderate numerical anchors are investigated. Similar to past results in attitude change, three separate data collections show that extreme anchors can have less influence on judgments than more moderate anchors. Though difficult to account for using traditional “anchor-and-adjust” and recent “selective accessibility” views, the findings are consistent with theories of attitude change. Implications of an attitude-change view of numerical anchoring are discussed.