We examined whether the sustained attention to response task is a better measure of response inhibition or sustained attention. Participants performed a number detection task for 37.3 min using either a Sustained Attention to Response Task (SART; high Go low No-Go) or a more traditionally formatted vigilance task (TFT; high No-Go low Go) response format. Participants performed these tasks using either a regular fixed ordered stimuli set (1-9, sequentially repeated), in which the target number appeared predictably, or a random order (1-9, random presentation), in which the target number appeared at random. We utilized functional near infrared spectroscopy (fNIRS) to measure cerebral oxygenation levels in the right and left frontal areas. We also used post-task participant reports of arousal, and conscious thoughts occurring during the tasks. Performance differed for the both response format and target predictability. Greater right than left frontal hemisphere activation occurred in the TFT than the SART with time-on-task. In addition, the SART response format resulted in elevated self-reports of task-related thoughts than the TFT response format. The results suggest the SART, random or fixed ordered, places high response inhibition, not necessarily sustained attention, demands on participants. Elevated levels of task-related thoughts during the SART format condition in comparison to the TFT condition does not appear to be in accord with the claim that the SART induces mindlessness. (Contains 7 figures.)