“Independent pilot study examining the connection between real-time drowsiness and cognitive task performance of varying complexity, and demonstrating the sensitivity of DANA to increased fatigue. Objectives: Determine whether caffeine weakens the positive associations between drowsiness and reduced cognitive function and whether such weakening effect fluctuates depending on the complexity of the cognitive task. Methods: 24 participants (12 males; 12 females; aged 18-31 years) were randomly allocated to either a placebo or caffeine group. Both groups received a 10-hour sleep opportunity and were then subject to 50 hours of total sleep deprivation (TSD). The caffeine group consumed 4 doses of caffeine every 2 hours on the first and second nights of TSD. Every 3 hours, all participants drove for 40 continuous minutes in a driving simulator. During the driving task, a randomly selected subgroup of 11 participants (5 from the caffeine group and 6 from placebo group) wore an infra-red oculography monitor that quantified drowsiness levels in the form of the Johns Drowsiness Scale (JDS) scores. After each driving task, all participants completed the following DANA tests: simple reaction time (SRT), procedural reaction time (PRT), and Go/No-Go (GNG). Results: Higher drowsiness (shown in increasing JDS scores) did not result in a linear decline in cognitive performance in the caffeine group. Further, the magnitude of this dissociation appeared to depend on task complexity, with caffeine significantly reducing the impact of drowsiness on executive performance in the GNG task, while producing similar but weaker trends in the PRT and SRT tasks. This is consistent with previous findings showing performance on simple tasks to be highly sensitive to sleep loss, while more complex tasks, such as response inhibition and decision making, tend to be less affected. Sensitivity of DANA: The results of the study demonstrate the sensitivity of DANA to detect changes in cognitive performance as a result of fatigue and caffeine.”