Is the Mind More Powerful Than the Heart? A Randomized Controlled Trial of Two Loving-Kindness Interventions

Context. Many spiritual traditions, like Buddhism, emphasize the importance of developing feelings of love and altruism toward others regardless of circumstances, but doing so can be challenging, especially in situations where individuals have little self-control resources, for example due to cognitive fatigue. These traditions offer techniques to train the mind, such as loving-kindness meditation, in order to facilitate the achievement of this altruistic goal. However, the evidence in favour of the prosocial benefits of loving-kindness meditation is scant and at times conflicting. Methods. To investigate the long-term effects of loving-kindness training on prosociality and aggression, we investigated changes in a range of prosocial variables at pre, post, and follow-up in a preregistered randomized controlled trial comparing three groups: loving-kindness meditation (N = 58), loving-kindness reflection (N = 53), and waitlist control (N = 92). Furthermore, to establish the robustness of the loving-kindness training relative to challenging circumstances such as cognitive fatigue, we introduced an ego depletion task at post-testing. Results. Planned contrasts analyses suggested effects on positive affect only for the meditation group, on self-reported compassion for both the meditation and reflection groups, and explicit social attitudes, aggressive behaviour, cognitive accessibility of a recent altruistic behaviour, willingness to help, only for the reflection group. There were no other group differences in attitudes toward aggression, dehumanization, implicit aggression, or charity donations. Moderation analyses revealed three-way interactions between group, implicit attitudes, and ego depletion, as hypothesized, but only for compassion and cognitive accessibility of a recent altruistic behaviour. Discussion. In conclusion, results suggest that the effects of reflecting on loving-kindness concepts provide robust and reliable prosocial effects, perhaps more than meditating on those concepts. Even those benefits are limited to certain behaviours, cognitions, or affects, and they do not generalize to many common behaviours such as charity donations. However, ego depletion seems to only moderate implicit attitudes when loving-kindness is embodied through meditation and not when it is confined to the intellectual mind.