Differentiating linked cognitive states under task demand and sleep restriction: toward an experimental framework for operational monitoring.

Real-world settings involve multiple interacting cognitive states such as mental workload, drowsiness, fatigue, and mind wandering, yet these are typically studied in isolation. A critical question is whether these states can be empirically differentiated given that they share overlapping behavioral and physiological signatures. We investigated whether task difficulty and sleep restriction produce dissociable effects across these states, and whether their response patterns reflect distinct underlying mechanisms or a common cognitive resource using a unified framework. Participants from operational populations (Study 1: n = 40; Study 2: n = 27) performed three complementary tasks (MATB-II, N-Back, and SART) under two manipulations: task difficulty and partial sleep restriction, targeting cognitive load and alertness. Increasing task difficulty degraded performance and increased perceived workload and fatigue across tasks. In contrast, sleep restriction primarily elevated subjective drowsiness and mind wandering, with smaller, task-dependent effects on performance. These findings provide evidence that cognitive and physiological states influencing situational awareness can be differentiated using complementary manipulations and characterized through distinct behavioral and subjective measures. This distinction provides a foundation for future predictive and monitoring approaches in applied settings.