Mindfulness training reduces slippery slope effects in moral decision-making and moral judgment.

Extant research has demonstrated the positive intrapersonal effects of mindfulness training. However, the cognitive mechanisms underlying the effects of mindfulness training on interpersonal processes are less clear. Here, we combined a randomized control mindfulness training design with computational approach to moral decision-making and moral judgments. Participants were randomly assigned to a Training group (N = 32) who received an 8-week mindfulness training or a Control group (N = 26) who waited for the same period of time. Before and after the 8-week period, participants completed a moral decision-making task, where they made tradeoff between money for themselves and unpleasant electric shocks to another person, and a moral judgment task, where they evaluated the blameworthiness of someone else's choices in the same moral decision-making task. Trait mindfulness, as measured by the Five-Facet Mindfulness Questionnaire, significantly increased from the pre- to post-training session for the Training group, but not the Control group, demonstrating the effectiveness of the mindfulness manipulation. For the Control group, participants' moral preference in both the decision-making task and the judgment task declined over time, exhibiting a "slippery slope" effect. In contrast, for the Training group, mindfulness training prevented moral preferences from declining. Computational modeling revealed that mindfulness training specifically reduced the increase in the weights of money over time in both the decision-making and judgment tasks, thereby curbing the "slippery slope" effects. These findings provide a cognitive account of the prosocial effects of mindfulness training on moral decision-making and moral judgments.