Abstract
A series of experiments was conducted to explore sources of difficulties in manipulating daily electronic appliances. In realizing users' goals, these appliances require users to decompose their goals to a set of subtasks in a specific way. We hypothesize that users who have extreme difficulties do not decompose the task or that their decompositions are different from the one that designers assume. To test this hypothesis, we compared the performance of those who had been taught the general idea of task decompsition with that of the control group, using a copy machine. The results of the two experiments showed that the trained group achieved the tasks faster with fewer errors than the control group. The experiment 3 examined this task decomposition hypothesis, using a refined copier that visualized the idea of task decompostion. The results showed that the refined copier reduced errors at the early stages of learning. These results strongly support the idea that users' difficulties lie mainly in the task decomposition.
