Discussion
In the present study, we combined a randomized control mindfulness training design with computational approach to moral decision-making and moral judgments. Without any active intervention, participants’ moral preference, both in decision-making and in moral judgment, declined over time, replicating the established moral slippery slope effectOne of the contributions of our study is that we provided evidence for a potential cognitive mechanism underlying the “moral slippery slope” and the potential effect of mindfulness training on it. By applying drift–diffusion modeling to the decision-making data, we showed that the decline in moral preference over time in the Control group is associated with an increase in the motivation to obtain money at the cost of harming another, rather than a decrease in the motivation to avoid harm. Importantly, the increase in such motivation was attenuated by mindfulness training, suggesting a potential cognitive mechanism underlying the prosocial effect of mindfulness training. This effect is consistent with previous findings showing that mindfulness training makes people attend to and accept the present moment, and reduces their motivation to seek external, material goodsA similar cognitive mechanism may also explain the effect mindfulness on moral judgment. By separating the effects of harm and monetary profits on moral judgment (cf.Several limitations of the present study should be noted. First, we adopted a set of strict pre-screening criteria, which led to relatively small sample sizes for both groups. Nevertheless, this sample size was equivalent to a previous study using the same moral decision-making task with a between-group designThe moral decision-making and judgment tasks and the computational framework behind them center around the theoretical conjecture that harm aversion constitutes utility in moral cognition. Harm aversion is a preference defined as a distaste for harming others. Admittedly, there has not been consensus regarding whether harm is the essence of moralityWe also noted that the pre-screening criteria were independent of the moral decision-making and judgment tasks. Although such sample sizes were comparable to a recent study using the same moral decision-making task and computational analysesTo conclude, by combining a randomized control mindfulness training design with computational approach to moral decision-making and moral judgments, we demonstrate that the moral slippery slope effect is driven primarily by an increase in the consideration of self-interest over time and that mindfulness training prevents the moral slippery slope by reducing such change. These findings provide a mechanistic account of the prosocial effects of mindfulness training on moral decision-making and moral judgments.