A system that infers and detects how focused a worker is on work tasks, based on physiological parameters collected using wearable and environmental sensors. The system can identify whether a worker is in a focused state of flow, the affective state in which the worker's mind is fully immersed and actively engaged in their task. The system can also identify whether the worker is anxious (where the task demands/difficulty is too high relative the worker's skills) or bored (where the task is too easy). Once the focus state is detected, the information can be used in various applications for optimizing the worker's tasks and work quality such as monitoring task mastery, interventions to improve worker focus (e.g., recommending breaks, reassigning tasks, clarifying goals), identifying potentially lower quality production lots in a manufacturing environment, measuring the effects of skills training, and personal informatics for improving a worker's own productivity.