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The Anti-Inference Bias and Circumstantial Evidence

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FOSW02 - Bayesian networks and argumentation in evidence analysis

My presentation will be based on two studies: Seeing is Believing: The Anti-Inference Bias, co-authored with Ilana Ritov and Doron Teichman (see here), and New Evidence about Circumstantial Evidence, co-authored with Elisha Harlev and Ilana Ritov (see here).

Judicial fact-finders are commonly instructed to determine the reliability and weight of any evidence, be it direct or circumstantial, without prejudice to the latter. Nonetheless, studies have shown that people are reluctant to impose liability based on circumstantial evidence alone, even when this evidence is more reliable than direct evidence. Proposed explanations for this reluctance have focused on factors such as the statistical nature of some circumstantial evidence, the tendency of fact-finders to assign low subjective probabilities to circumstantial evidence, and the fact that direct evidence can rule out with greater ease any competing factual theory regarding liability.

In the first article, we demonstrated experimentally that even when these factors are controlled for, the disinclination to impose liability based on non-direct evidence remains. For instance, people are much more willing to convict a driver of a speeding violation on the basis of a speed camera than on the basis of two cameras documenting the exact time a car passes by them — from which the driver’s speed in the pertinent section of the road is inferred. While these findings do not necessarily refute the previous theories, they indicate that they are incomplete. The new findings point to the existence of a deep-seated bias against basing liability on inferences — an anti-inference bias.  

The second article describe seven new experiments that explore the scope and resilience of the anti-inference bias. It shows that this bias is significantly reduced when legal decision-makers confer benefits, rather than impose liability. We thus point to a new legal implication of the psychological phenomenon of loss aversion. In contrast, we find no support for the hypothesis that the reluctance to impose legal liability on the basis of circumstantial evidence correlates with the severity of the legal sanctions. Finally, the article demonstrates the robustness of the anti-inference bias and its resilience to simple debiasing techniques.

Taken together, the studies show that the anti-inference bias reflects primarily normative intuitions, rather than merely epistemological ones, and that it reflects conscious intuitions, rather than wholly unconscious ones. The articles discuss the policy implications of the new findings for procedural and substantive legal norms, including the limited potential (and questionable desirability) of debiasing techniques, the role of legal presumptions, and the advantages of redefining offenses in a way that obviates the need for inferences.

This talk is part of the Isaac Newton Institute Seminar Series series.

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