What Mind Wandering Reveals About Executive-Control Abilities and Failures

People's minds sometimes wander from ongoing activities. Although these experiences can be pleasant and useful, they are often unintentional and precipitate mistakes. In this article, we adopt an individual-differences perspective in considering unwanted mind wandering as an indicator of both momentary failures of and enduring deficiencies in executive-control functions. We describe research that associates normal variation in working memory capacity (WMC)-a cognitive ability that broadly predicts intellectual capabilities and accomplishments-with off-task thinking. In laboratory and daily-life assessments, people with lower WMC mind wander more frequently than do those with higher WMC, at least during demanding tasks. Moreover, the error-proneness of lower-WMC subjects seems to arise partly from their vulnerability to mind wandering. Executive control over one's thoughts therefore seems to contribute to the effective regulation of behavior.