• Not mentally demanding at all: There is enough spare capacity For all desirable additional tasks.
• Slightly mentally demanding: There is a little spare capacity (level of effort allows little attention to additional tasks and maintenance of effort in the primary task not in question)
• Moderately mentally demanding: Reduced spare capacity (Additional tasks cannot be given the desired amount of attention)
• Very mentally demanding: Almost no spare capacity/Insufficient spare capacity (Difficulty in maintaining the level of effort in the primary task due to Very high workload) 
• Extremely mentally demanding: There is no spare capacity (Serious doubts as to the ability to maintain the level of effort in the primary task due to an extremely high workload)