The effects of sleep deprivation on cognitive performance psychological variables related to cognitive performance were studied in 44 college students. Participants completed the Watson-Glaser Critical Thinking Appraisal after either 24 hours of sleep deprivation or approximately 8 hours of sleep. After completing the cognitive task, the participants completed 2 questionnaires, one assessing self-reported effort, concentration, and estimated performance, the other assessing off-task cognitions. As expected, sleep-deprived participants performed significantly worse than the nondeprived participants on the cognitive task. However, the sleep-deprived participants rated their concentration and effort higher than the nondeprived participants did. In addition, the sleep-deprived participants rated their estimated performance significantly higher than the nondeprived participants did. The findings indicate that college students are not aware of the extent to which sleep deprivation negatively affects their ability to complete cognitive tasks.