• Physical comfort : If you do not like to touch an item you won't. If you do not touch it you will not operate it. If you do not operate it, then it is useless.
• The utility of an item is the only true measure of the quality of its design.
• The mental aspect of comfort in the human-machine interface is found in feedback.
What is efficiency?
• Efficiency is quite simply making something easier to do.
• Reducing the strength required makes a process more physically efficient.
• Reducing the number of parts makes repairs more efficient.