Processes Underlying Human Performance
Lisanne Bainbridge University College London
Two decades ago, a chapter on aviation with this title might have focused on physical aspects of human performance, on representing the control processes involved in flying. There has been such a fundamental change in our knowledge and techniques that this chapter focuses almost exclusively on cognitive processes. The main aims are to show that relatively few general principles underlie the huge amount of information relevant to interface design, and that context is a key concept in understanding human behavior.
Classical interface human factors/ergonomics consists of a collection of useful but mainly disparate facts and a simple model of the cognitive processes underlying behavior--that these processes consist of independent information-decision-action or if--then units. (I use the combined term human factors/ergonomics, shortened to HF/E, because these terms have different shades of meaning in different countries. Cognitive processing is the unobservable processing between arrival of stimuli at the senses and initiating an action.) Classic HF/E tools are powerful aids for interface design, but they make an inadequate basis for designing to support complex tasks. Pilots and air traffic controllers are highly trained and able people. Their behavior is organized and goal-directed, and they add knowledge to the information given on an interface in two main cognitive activities: understanding what is happening, and working out what to do about it.
As the simple models of cognitive processes used in classic HF/E do not contain reminders about all the cognitive aspects of complex tasks, they do not provide a sufficient basis for supporting HF/E for these tasks. The aim of this chapter is to present simple concepts that could account for behavior in complex dynamic tasks and provide the basis for designing to support people doing these tasks. As the range of topics and data that could be covered is huge, the strategy is to indicate key principles by giving typical examples, rather than attempting completeness. This chapter does not present a detailed model for the cognitive processes suggested, or survey HF/E techniques, and it does not discuss collective work. The chapter offers three main sections, on simple use of interfaces; understanding, planning, and multitasking; and learning, workload, and errors. The conclusion outlines how the fundamental nature of human cognitive processes underlies the difficulties met by HF/E practitioners.