## 1 Introduction  
Sustained attention--the capacity to maintain focus and respond to stimuli over extended periods--is a foundational component of human cognitive performance. It is critical in numerous real-world settings, such as driving, medical monitoring, and industrial operations, where lapses in attention can lead to errors, accidents, or even life-threatening consequences. Among the tools developed to quantify and assess sustained attention, the psychomotor vigilance task (PVT) has emerged as a gold standard due to its simplicity, reliability, and sensitivity to fatigue and circadian influences [1, 2, 3]. The PVT is commonly used in research on sleep deprivation, shift work, and cognitive aging, making it a key instrument in both experimental psychology and applied fields such as occupational health and transportation safety [4, 5, 6, 7]. The ability to sustain attention varies widely across individuals. These individual differences are shaped by both intrinsic and extrinsic factors. Age is one of the well-documented determinants, with research consistently showing that older adults tend to exhibit slower reaction times and more attentional lapses compared to younger individuals [8; 9; 10; 11]. This decline in vigilance performance with age has been linked to broader changes in cognitive processing speed, executive functioning, and arousal regulation. However, while age-related trends are relatively well understood, the effects of other demographic and situational variables, such as sex and the time of day when a task is performed, remain less thoroughly investigated in the context of sustained attention. Biological sex may influence attentional processes through a variety of mechanisms, including hormonal cycles, stress reactivity, and differences in sleep patterns [12; 13; 14; 15; 16; 17; 18; 19]. Some studies have reported subtle but significant differences in attentional control and vigilance performance between men and women, although the findings are often inconsistent or underpowered due to small sample sizes. Furthermore, the time of day is a crucial but frequently overlooked factor. Human cognitive performance follows circadian rhythms, which affect alertness and response capabilities throughout the day [20; 21; 22; 23; 24; 25]. Morning and late afternoon may show differing patterns of attentional capacity due to natural fluctuations in sleep pressure and arousal levels. Understanding how these temporal effects interact with individual characteristics such as age and sex is essential for developing a more nuanced and generalizable model of sustained attention. Despite the importance of individual and contextual factors in shaping cognitive performance, comprehensive datasets that allow for the concurrent evaluation of age, sex, and time-of-day effects on psychomotor vigilance task (PVT) performance remain scarce. Prior research has shown that sustained attention can decline with aging and that performance on vigilance tasks is sensitive to circadian influences and potentially sex differences. However, most existing studies examine these variables in isolation or within limited demographic samples, thereby reducing their applicability to real-world scenarios where multiple factors interact dynamically to influence attention. To address this gap, the present study analyzes PVT performance data from a diverse sample of 356 participants, incorporating metrics such as the mean reaction time (RT), minor and major lapses, and false starts. Participants were tested at different times of day (morning, early afternoon, late afternoon), and demographic variables such as age and sex were also recorded. This multidimensional dataset allows for the simultaneous investigation of how biological (age, sex) and contextual (time of day) factors contribute to sustained attention. Based on prior findings, we advance the following hypotheses.