ABSTRACT
Although the sophistication of technology has increased dramatically during the latter half of the 20th century, the importance of the human operator has not diminished. On the contrary, the uneasy symbiosis between people and machines often creates situations where operator performance is the only defence against unwanted consequences. A grow ing number of essential technological systems rely on the interaction between people and machines to accomplish their purpose, so they depend on adequate human perform ance. The proper specification of the man-machine interaction (MMI) is therefore a central issue in man-machine systems (MMS) design, and this has created a need to improve the underlying concepts and models.
