Mental Fatigue

A state of reduced cognitive capacity resulting from prolonged mental effort, characterized by difficulty concentrating, slower processing, increased errors, and reduced ability to handle unexpected situations. Mental fatigue particularly affects people with dementia, traumatic brain injury, and other cognitive disabilities. In usability testing, mental fatigue requires mandatory breaks (for sessions over 30 minutes), limited task numbers per session, and flexibility to pause or stop. Mental fatigue can invalidate time-based performance metrics.