A computational modeling approach to investigating mind wandering-related adjustments to gaze behavior during scene viewing.

Research on gaze control has long shown that increased visual-cognitive processing demands in scene viewing are associated with longer fixation durations. More recently, though, longer durations have also been linked to mind wandering, a perceptually decoupled state of attention marked by decreased visual-cognitive processing. Toward better understanding the relationship between fixation durations and visual-cognitive processing, we ran simulations using an established random-walk model for saccade timing and programming and assessed which model parameters best predicted modulations in fixation durations associated with mind wandering compared to attentive viewing. Mind wandering-related fixation durations were best described as an increase in the variability of the fixation-generating process, leading to more variable-sometimes very long-durations. In contrast, past research showed that increased processing demands increased the mean duration of the fixation-generating process. The findings thus illustrate that mind wandering and processing demands modulate fixation durations through different mechanisms in scene viewing. This suggests that processing demands cannot be inferred from changes in fixation durations without understanding the underlying mechanism by which these changes were generated.