External resources sometimes change human performance drastically. Previous researches have explained this effect of external resources as a reduction of memory load or calculation load. D. A. Norman criticises this approach as “System View,” and proposes “Personal View” as an alternative. This latter approach assumes that external resources transform the original task. Based on this idea, Norman and his colleague have developed representational analysis to capture the characteristics of external resources.
However, representational analysis ignores cognitive agents. When external resources transform a task, knowledge and skills required to solve the task are also changed. If a cognitive agent doesn't possess these knowledge and skills, transformed task doesn't become easier compared with original one. This means that difficulty of the transformed task is determined not only by the characteristics of the task captured by representational analysis, but also by the knowledge and skills possessed by a cognitive agent.
In addition, transformation of task sometimes requires transformation of cognitive agents. From this point of view, three issues are discussed. First, changing task definition is an important ability. Second, change of task in learning situation changes what skill is acquired. Third, change of cognitive agent is influenced by culture.