This paper presents a theoretical analysis of the relationships between the requirements of a
computerized task and people's knowledge of this task outside the computer system. The
analysis is based on the goals to be reached, the methods which may be used, and the
conditions which must be satisfied for each method to be used, with or without the computer
system. It is suggested that it will be most difficult to learn a computerized task when new
methods are related to old goals and/or when old methods require new conditions to be …