The Apple Desktop Interface provides a consistent and familiar computer environment in which people can perform their many tasks. People aren't trying to use computers , they're trying to get their jobs done.
Given this focus on people and their tasks, the Apple Desktop Interface has had to assume a model of people, in order to suit the interface to them. People, however, are delightfully complex and varied, which assures that a theory of human activity that would provide a complete framework for the design of human-computer interaction is a long way off. Such a theory would be oversimplified anyway, because computers themselves change the way we think, feel and behave. Computer design and human activity must therefore evolve together. Apple believes that caring how people behave will help computer designers provide a consistent world that a person can enter with ease and effectiveness, even though many of the details of human activity are not understood.
The Apple Desktop Interface is based on the assumption that people are instinctively curious: they want to learn and they learn best by active self-directed exploration of their environment. People strive to master their environment: they like to have a sense of control over what they are doing, to see and understand the results of their own actions. People are also skilled a manipulating symbolic representations: they love to communicate in verbal, visual and gestural languages. Finally, people are both imaginative and artistic when they are provided with a comfortable context; they are most productive and effective when the environment in which they work and play is enjoyable and challenging [Appl 87].