Breakdown of utilitarian moral judgement after basolateral amygdala damage

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 119; no. 31; pp. 1 - 7
• Main Authors: van Honk, Jack, Terburg, David, Montoya, Estrella R., Grafman, Jordan, Stein, Dan J., Morgan, Barak
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 02.08.2022
• Subjects: Algorithms; Amygdala; Basolateral Nuclear Complex; Biological Sciences; Breakdown; Damage; Decision Making; Ethics; Humans; Judgment; Morals; Neuroscience; Psychological and Cognitive Sciences; Rodents; Social Sciences; basolateral amygdala; social decision-making; computational framework; moral judgement; brain lesion
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2119072119

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.