In this study, we examined the hypothesis that masked general action and inaction cues that are processed during a cognitive task directly mobilize effort exerted during the task. Participants were randomly assigned to an action-prime condition, an inaction-prime condition, or a control condition and performed a Sternberg short-term memory task. The intensity of effort the participants exerted during the task was estimated by measuring their heart responses (cardiac preejection period, PEP) during task performance. As expected, exposure to masked action cues resulted in stronger PEP reactivity than exposure to masked inaction cues. PEP reactivity in the control group fell in between reactivity when action cues were used and reactivity when inaction cues were used. Participants' task performance revealed a corresponding pattern: Reaction times were the shortest in the action-prime condition, increased in the control condition, and increased further in the inaction-prime condition. These results show that masked action cues and inaction cues directly influence the intensity of effort exerted in the performance of a task.