Effort Mobilization and Lapses of Sustained Attention.

The current study examined whether effort mobilization would enhance sustained attention and reduce lapses of attention. Participants performed a sustained attention task and were randomly assigned to either an effort condition where they were instructed to "Try Hard" on a subset of trials or were assigned to a control condition with no "Try Hard" instructions. Pupillary responses were continuously recorded, and periodically during the task participants were presented with thought probes to determine whether they were on or off task. The results suggested within the effort condition there were no behavioral differences between Try Hard and "Standard" trials. Preparatory pupil responses were increased in Try Hard trials, but there were no differences for phasic pupillary responses to stimulus onset. In contrast, examining differences between the effort and control conditions suggested that participants who received the Try Hard instructions demonstrated faster overall performance, a reduction in very long reaction times, and reported fewer off-task thoughts compared with participants in the control condition. Participants in the effort condition also demonstrated a larger ramp-up in pupillary responses during the preparatory interval and a larger phasic response to stimulus onset compared with participants in the control condition. These results are consistent with attention allocation models suggesting that participants in the effort condition mobilized more attentional effort than participants in the control condition, resulting in enhanced sustained attention and a reduction in lapses of attention. These results also are consistent with recent theories, which suggest that the locus coeruleus norepinephrine system is associated with effort mobilization.