Answer:
Practice; fatigue.
Step-by-step explanation:
The concepts of practice effect and fatigue effect are one of the Important aspects on cognitive development or cognitive tasks in Psychology.
The General saying is that Practice makes perfection and this is what the concept of practice effect is based upon. The more you do or practice something, the greater your success rate for instance now the more you practice a particular sport, the more you improve and discover new techniques and you become more efficient.
Not all practice can lead to efficiency because sometimes when you do more of something it might lead to fatigue that is you been tired more. Practice effect helps in the development of Human beings while fatigue effect do not.