A commonly studied domain is chess playing. It is particularly suitable since it lends itself to representation in terms of problem space thoery, in which the intial board configuration and the final position constitute the states while the moves appeared as transition operators. Masters took lesser time than novices to react to a situtation and produced better moves. This is largely because chess masters remember board configurations and good moves associated with them. They can chunk the board configuration in order to hold it in short-term memory.
Skilled behavior becomes automatic over a period of time.
Experts tend to mentally rehearse their actions in order to identify exactly what they do. Althoug such skilled behavior is efficient it may cause errors when the context of the activity changes. The psychological principles and properties that have been discussed apply to the majority of people. However, there are individual differences which affect a small percentage. The differences may be long term such as sex, physical capabilities and individual capabilities.