Editing Workload (section)

===Theories===
[[File:KTS1workload.jpg|thumb|Figure 1: Wickens' Multiple Resource Theory (MRT) Model]]
Wickens' (1984) multiple resource theory (MRT) model <ref>Wickens, C.D. (1984). "Processing resources in attention", in R. Parasuraman & D.R. Davies (Eds.), ''Varieties of attention'', (pp. 63–102). New York: Academic Press.</ref> is illustrated in figure 1:

Wickens' MRT proposes that the human operator does not have one single information processing source that can be tapped but several different pools of resources that can be tapped simultaneously. Each box in figure 1 indicates one cognitive resource. Depending on the nature of the task, these resources may have to process information sequentially if the different tasks require the same pool of resources or can be processed in parallel if the task requires different resources.

Wickens' theory views performance decrement as a shortage of these different resources and describes humans as having limited capability for processing information. Cognitive resources are limited, and a supply and demand problem occurs when the individual performs two or more tasks that require a single resource (as indicated by one box on the diagram). Excess workload caused by a task using the same resource can cause problems, errors, or slower performance. For example, if the task is to dial the phone, then no excess demands are placed on any component. However, if another task is being performed simultaneously that demands the same component(s), the result may be an excess workload.

The relationship between workload and performance is complex. It is not always the case that as workload increases, performance decreases. Performance can be affected by workload being too high or too low (Nachreiner, 1995). A sustained low workload (underload) can lead to boredom, loss of situation awareness and reduced alertness. Also, as workload increases, performance may not decrease as the operator may have a strategy for handling task demands.

Wickens' theory allows system designers to predict when:
* Tasks can be performed concurrently.
* Tasks will interfere with each other.
* Increases in the difficulty of one task will result in a loss of performance of another task.

Like Wickens, McCracken and Aldrich (1984) describe the processing, not as one central resource but as several processing resources: visual, cognitive, auditory, and psychomotor (VCAP). All tasks can be decomposed into these components.
* The visual and auditory components are external stimuli that are attended to.
* The cognitive component describes the level of information processing required.
* The psychomotor component describes the physical actions required.

They developed rating scales for each VCAP component, which provide a relative rating of the degree to which each resource component is used.

Joseph Hopkins (unpublished) developed a training methodology. The background to his training theory is that complex skills are, in essence, resource conflicts where training has removed or reduced the conflicting workload demands, either by higher-level processing or by predictive time sequencing. His work is based on Gallwey (1974) and Morehouse (1977). The theory postulates that the training allows the different task functions to be integrated into one new skill. An example of this is learning to drive a car. Changing gear and steering are two conflicting tasks (i.e. both require the same resources) before they are integrated into the new skill of "driving". An experienced driver will not need to think about what to do when turning a corner (higher level processing) or may change gear earlier than required to give sufficient resources for steering around the corner (predictive time sequencing).