Who is prone to wander and when? Examining an integrative effect of working memory capacity and mindfulness trait on mind wandering under different task loads

•One’s tendency to mind wandering is determined by mindfulness trait and WMC.•Mindful people have fewer mind wanderings in both demanding and undemanding tasks.•WMC only predicts unaware and unintentional mind wanderings under a demanding task.•Mindfulness predicts aware and unintentional mind wanderings under a demanding task.•Mindfulness predicts all four types of mind wandering in an undemanding task. We proposed an integration hypothesis of mind wandering in which the tendency of mind wandering is only related to working memory capacity (WMC) when a self-regulation process is required (i.e., under a high task load); however, this tendency is related to mindfulness regardless of task load. A within-group experiment with 160 participants was conducted. Task load was manipulated as high or low using modified 0-back and 2-back tasks, during which participants’ self-caught mind wanderings and the types of mind wandering (aware vs. unaware; intentional vs. unintentional) were measured. The results supported our hypothesis that WMC was negatively associated with mind wandering only in demanding tasks, and mindfulness scores were negatively associated with mind wandering across tasks. Furthermore, we also determined how WMC and the mindfulness trait were related to different types of mind wandering. Theoretical implications were discussed.