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Wednesday, January 25, 2023

Outcome effects, moral luck and the hindsight bias

M. Kneer & I. Skoczen
Volume 232, March 2023, 105258


In a series of ten preregistered experiments (N = 2043), we investigate the effect of outcome valence on judgments of probability, negligence, and culpability – a phenomenon sometimes labelled moral (and legal) luck. We found that harmful outcomes, when contrasted with neutral outcomes, lead to an increased perceived probability of harm ex post, and consequently, to a greater attribution of negligence and culpability. Rather than simply postulating hindsight bias (as is common), we employ a variety of empirical means to demonstrate that the outcome-driven asymmetry across perceived probabilities constitutes a systematic cognitive distortion. We then explore three distinct strategies to alleviate the hindsight bias and its downstream effects on mens rea and culpability ascriptions. Not all strategies are successful, but some prove very promising. They should, we argue, be considered in criminal jurisprudence, where distortions due to the hindsight bias are likely considerable and deeply disconcerting.


• In a series of ten studies (N = 2043) we examine the relation between moral luck, negligence and probability

• Most people deem outcome irrelevant for ascriptions of negligence & blame in WS studies, so there’s no “puzzle of moral luck”

• In between-subjects designs, the effect of luck on negligence and blame seems to be driven by the hindsight bias

• We examine three strategies to alleviate the hindsight bias on perceived probability, negligence and blame

• Two alleviation strategies significantly decrease the hindsight bias and could potentially be used in legal trials


In a series of experiments with 2043 participants, we explored the effect of outcome on judgments of subjective and objective probability, mens rea and culpability. For mens rea and blame attributions (though not for deserved punishment), the outcome effect constitutes a bias. The distorted assessment of mens rea and blame, we showed, is ultimately rooted in the hindsight bias: People tend to assess a potential harm as more likely when it does come to pass than when it does not; they therefore ascribe more negligence to the agent, and consequently consider him more culpable.

Echoing the literature from behavioral economics and legal psychology, we argued that the downstream effects of the hindsight bias constitute a serious threat to the just adjudication of legal trials, in particular in countries where mens rea is determined by lay juries (such as the US and the UK). And although it is well established that the hindsight bias is pervasive and difficult to overcome, we have shown that there are measures to reduce its impact. Among a series of different debiasing strategies we have put to the test, we showed that expert probability stabilizing (which, on occasion, is already in use in courts) and entertaining counterfactual outcomes hold considerable promise. We would strongly urge further research conducted jointly with legal practitioners that explores the most suitable ways of introducing (or further implementing) these techniques in the courtroom, so as to make the law more just and equal.