DesignOfEverydayThings - Feedback

• Anti-ex. or repeatedly push the pedestrian button at a street crossing? => Because user doesn't know whether system got his request or not.
• Feedback—communicating the results of an action—is a well-known concept from the science of control and information theory.
• You can't hit a ball without seeing the target
• You can't pick up a glass with hand without the feedback.
  
• Feedback must be immediate: even a delay of a tenth of a second can be disconcerting. If the delay is too long, people often give up, going off to do other activities. 
• It wastes resource to do one thing that user doesn't wait for it anymore.
• Too much feedback become annoying. 
• Ex. When performance tuning, we need major number to alarm. It will be useless if we alarm everything
• Backseat driver: too much feedback to driver. May distract people or just turn it off
• Use one simple signal producer to reduce cost, let people not easy to remember (Beep code)
• Beep code definition may be different in different machines. We'll be confused when those machines beep together.
• Feedback has to be planned and prioritized. 
• Feedback is essential, but it has to be done correctly. Appropriately.