We stated: “The nature of people’s activities explained 4.6% of the within-person variance in happiness and 3.2% of the between-person variance in happiness, but mind-wandering explained 10.8% of within-person variance in happiness and 17.7% of between-person variance in happiness.” To compute the within-person variation, happiness scores were centered on each person's mean happiness. Then, OLS regression was used at the sample level to analyze the amount of within-person variance in happiness explained by mind- wandering and by activity. To compute the between-person variation, person-level mean values of happiness, proportion of time spent in each mind-wandering state, and proportion of time spent in each activity were computed. Then, OLS regression was used at the person level to analyze the amount of between-person variance in happiness explained by mind-wandering and by activity.