Breakdown of utilitarian moral judgement after basolateral amygdala damage

Abstract

Most of us would regard killing another person as morally wrong, but when the death of one saves multiple others, it can be morally permitted. According to a prominent computational dual-systems framework, in these life-and-death dilemmas, deontological (nonsacrificial) moral judgments stem from a model-free algorithm that emphasizes the intrinsic value of the sacrificial action, while utilitarian (sacrificial) moral judgments are derived from a model-based algorithm that emphasizes the outcome of the sacrificial action. Rodent decision-making research suggests that the model-based algorithm depends on the basolateral amygdala (BLA), but these findings have not yet been translated to human moral decision-making. Here, in five humans with selective, bilateral BLA damage, we show a breakdown of utilitarian sacrificial moral judgments, pointing at deficient model-based moral decision-making. Across an established set of moral dilemmas, healthy controls frequently sacrifice one person to save numerous others, but BLA-damaged humans withhold such sacrificial judgments even at the cost of thousands of lives. Our translational research confirms a neurocomputational hypothesis drawn from rodent decision-making research by indicating that the model-based algorithm which underlies outcome-based, utilitarian moral judgements in humans critically depends on the BLA.

The Implications of Moral Neuroscience for Brain Disease: Review and Update

“…Another theoretical approach to morality, the dual process model , incorporates both moral intuitions and moral reasoning into normative rules or principles on how you should behave. These normative rules are either deontological (emotionally based) norms that are absolute moral codes regardless of outcome or utilitarian (the ends justify the means) norms that weigh costs and benefits for the best outcome for the greater many (van Honk et al, 2022).…”

“…Therefore, damage to the amygdala may result in decreased emotional aversiveness to harmful utilitarian actions and in overly cooperative and trusting behavior (Koscik and Tranel, 2011; Shenhav and Greene, 2014). However, focal damage to the basolateral nuclei of the amygdala, which is involved in evaluating emotional significance, has resulted in extreme withholding of utilitarian judgments, possibly from the disinhibition of autonomic responses (van Honk et al, 2022). Ultimately, the amygdala–VMPFC axis integrates moral judgments with emotional assessments rather than with utilitarian ones; dysfunction of this axis can result in immoral behavior (Shenhav and Greene, 2014).…”

A view from mindreading on fast-and-slow thinking

“…Cushman and colleagues have since provided compelling evidence that utilitarian judgments are model-based, while deontological judgments are driven by model-free responses (Miller & Cushman, 2013;Patil et al, 2021). Moreover, the model-based/ model-free distinction specifically explains why patients with hippocampal damage and basolateral amygdala damage make fewer utilitarian judgments (McCormick et al, 2016;van Honk et al, 2022). As Cushman emphasizes, model-based judgment is not emotion free, as value must be attached to outcomes.…”

Dual-process moral judgment beyond fast and slow

“…(But see Craver et al, 2016.) Finally, and most recently, van Honk et al (2022) show that patients with damage to the basolateral amygdala (implicated in goal-directed decision making) is associated with increased deontological judgment. And here, too, the effects appear to be because of dominant emotional responses.…”

“…Cushman and colleagues have since provided compelling evidence that utilitarian judgments are model-based, while deontological judgments are driven by model-free responses (Miller & Cushman, 2013; Patil et al, 2021). Moreover, the model-based/model-free distinction specifically explains why patients with hippocampal damage and basolateral amygdala damage make fewer utilitarian judgments (McCormick et al, 2016; van Honk et al, 2022). As Cushman emphasizes, model-based judgment is not emotion free, as value must be attached to outcomes.…”