Highly motivated students often exhibit better academic performance than less motivated students. However, to date, the specific cognitive mechanisms through which motivation increases academic achievement are not well understood. Here we explored the possibility that mind wandering mediates the relation between motivation and academic performance, and additionally, we examined possible mediation by both intentional and unintentional forms of mind wandering. We found that participants reporting higher motivation to learn in a lecture-based setting tended to engage in less mind wandering, and that this decrease in mind wandering was in turn associated with greater retention of the lecture material. Critically, we also found that the influence of motivation on retention was mediated by both intentional and unintentional types of mind wandering. Not only do the present results advance our theoretical understanding of the mechanisms underlying the relation between motivation and academic achievement, they also provide insights into possible methods of intervention that may be useful in improving student retention in educational settings.Keywords Mind wandering . Motivation . Intentional mind wandering . Unintentional mind wandering . Lectures It has been well established that motivation is a key determinant of academic achievement, with more highly motivated students typically outperforming their less motivated colleagues (e.g., Pintrich, 1999;Schiefele, Krapp, & Winteler, 1992). However, to date, the specific cognitive mechanism(s) through which motivation influences academic achievement are not well understood, and only recently has research begun to systematically explore such mechanisms. In one such study, it was suggested that the relation between motivation and academic performance is mediated by mind wandering: specifically, that poorly motivated students frequently engage in mind wandering, which in turn results in poorer retention (Unsworth & McMillan, 2013). Here we further refine this theoretical proposal by examining whether the relation between motivation and retention might be differentially associated with intentional and unintentional forms of mind wandering. In addition, we expand previous research on the relations among motivation, mind wandering, and retention by examining the effects of these variables in a novel educational context-namely, during a lecture. Thus, the present investigation both advances our theoretical understanding of the mechanism(s) underlying the relation between motivation and academic achievement and generalizes this research to a novel educational context.In recent work, Unsworth and McMillan (2013) explored the effects of motivation and mind wandering on reading comprehension in a laboratory setting. To this end, the researchers had participants read part of a chapter from a textbook, and while reading, the participants were occasionally presented with thought probes to assess whether they were "mind wandering" or Bfocused on the task.^Following the reading task,...