Reduced Alertness: Feeling drowsy or less vigilant.

Difficulty Concentrating: Challenges in maintaining focus on tasks.

Slower Cognitive Processing: Longer reaction times and decision-making.

Irritability or Mood Changes: Increased susceptibility to frustration.

Physical Sensations: Headaches or a feeling of heaviness in the head.

Physical Performance: Mental fatigue can impair performance in both cognitive and physical tasks and is distinct from physical fatigue, although the two can interact and exacerbate each other.