<p>Attention lapses occur when focus shifts away from the task at hand towards internal or external distractions and can lead to failures in completing intended actions. Goal-setting theory proposes that setting specific, difficult goals leads to better task performance over vague goals. The present study examined whether goal setting increased attentional effort and reduced attention lapses during a four-choice reaction time task. The control condition received the vague goal: “respond as quickly as possible while keeping your accuracy above 95%.” The goal condition received specific goals that became progressively harder over time (450 ms, 400 ms, and 350 ms) with the same accuracy goal. Pupillary responses were recorded throughout and subjects answered randomly presented thought probes to determine whether they were experiencing task-unrelated thoughts (TUTs). The goal condition displayed larger preparatory and phasic pupil responses, suggesting more attentional effort was exerted during the task. In addition, the goal condition displayed fewer attention lapses both behaviorally and with TUTs. Further, several typical time-on-task effects were mitigated or eliminated (shown in behavioral, subjective, and physiological measures). The results reinforce previous findings that goal-setting techniques can reduce attention lapses and indicate attentional effort is a mechanism behind the efficacy of goal setting.</p>