“Given that only participants whose minds had wandered at pretesting could measurably improve their focus, we next examined whether improvement in WMC and GRE performance following mindfulness training was mediated by reduced mind wandering specifically among participants who were prone to mind wandering at pretesting. Following Preacher, Rucker, and Hayes (2007), we ran a test of moderated mediation examining whether the effect of condition on change in performance (an average of changes in the proportion of correct responses on the WMC and GRE measures) was mediated by change in mind wandering (an average of z-score-standardized changes in probe-caught and retrospectively self-reported mind wandering) specifically for participants with high levels of baseline mind wandering (an average of z-score standardized probe-caught and retrospectively self reported mind wandering at pretesting; see Table 1)....Change in mind wandering therefore significantly mediated the effect of mindfulness training on change in performance among participants
who exhibited a tendency to mind-wander at pretesting.”
So it seems that the effect will probably be best for those who have the most mind-wandering at baseline.
An excellent question. From the article:
“Given that only participants whose minds had wandered at pretesting could measurably improve their focus, we next examined whether improvement in WMC and GRE performance following mindfulness training was mediated by reduced mind wandering specifically among participants who were prone to mind wandering at pretesting. Following Preacher, Rucker, and Hayes (2007), we ran a test of moderated mediation examining whether the effect of condition on change in performance (an average of changes in the proportion of correct responses on the WMC and GRE measures) was mediated by change in mind wandering (an average of z-score-standardized changes in probe-caught and retrospectively self-reported mind wandering) specifically for participants with high levels of baseline mind wandering (an average of z-score standardized probe-caught and retrospectively self reported mind wandering at pretesting; see Table 1)....Change in mind wandering therefore significantly mediated the effect of mindfulness training on change in performance among participants who exhibited a tendency to mind-wander at pretesting.”
So it seems that the effect will probably be best for those who have the most mind-wandering at baseline.