Academic journal article Human Factors

The Utility of Display Space in Keeping Track of Rapidly Changing Information

Academic journal article Human Factors

The Utility of Display Space in Keeping Track of Rapidly Changing Information

Article excerpt


Human operators whose jobs involve scheduling, coordinating, and keeping track of process variables that interact with each other often support these tasks by augmenting their work environments with external memory aids such as computer displays, strip charts, labels, and job aids. In these environments, external information, particularly the spatial location in which information appears, serves a vital role in fostering situational awareness (Endsley, 1994; Sarter & Woods, 1991, 1994; Segal & Andre, 1995) and in supporting operators' abilities to encode, maintain, and retrieve information.

However, as older systems and displays are reengineered and automated, many physical devices are replaced with "soft" computer displays, which present different information in the same place over time. In such soft-display environments, the performance benefits of having information appear consistently in a unique physical space may be lost. Despite extensive research on the kinds and quantities of information that can be encoded and maintained in different working-memory (WM) systems (Baddeley, 1986; Baddeley & Hitch, 1974, 1994; Schneider & Detweiler, 1987), the types of interference that can occur when two or more tasks are performed concurrently (Ogden, Levine, & Eisner, 1979; Wickens, 1980, 1984, 1991; Wickens & Liu, 1988), and the consequences of different types of rehearsal on retention (Craik & Lockhart, 1975; Craik & Watkins, 1972), contemporary memory research has produced few results that specifically address how a task's spatial layout influences memory for rapidly changing information. With the experiments described in this paper, we seek to fill this gap.

Past research suggests that spatial information can play a beneficial role in supporting memory. For instance, the method of loci, a well-known mnemonic (Yates, 1966), has long been used to increase memory for stories and ordered lists of items. Several variations exist but, in general, loci mnemonics involve associating items to be remembered with a previously memorized and ordered set of objects, such as locations in a familiar environment. At recall, items are retrieved by taking an imaginary walk through the environment, using the locations as retrieval cues. This method takes advantage of a consistent and well-learned set of retrieval cues (the locations) to aid memory for ordered information (e.g., a speech or grocery list).

In jobs requiring operators to monitor and keep track of changing values or attributes of task-relevant objects, it is likely that memory aids similar to the method of loci exist and are supported by consistent, well-learned structure in the work environment. In process control, for example, indicators are often grouped close to one another in space because they indicate state variables for the same environmental object (component or subsystem) or because they are fed by sensors from a single subsystem. In a power plant, for instance, temperature, pressure and flow indicators for a steam header outside the boiler may be grouped in close physical proximity. The steam header in this case is an invariant part of the machinery, or an object in the environment, whereas the multiple indicators present variable values, or attributes, of that object (temperature, pressure, and flow of steam through the header). Alternatively, the layout of indicators may be organized around principles such as type/attribute (e.g., all temperature sensors appear together) or function/task (e.g., all indicators relevant to a start-up sequence appear together).

Regardless of the organization, over time, users learn and come to rely on consistencies in the layout and develop strategies that rely on this structure for monitoring and retrieving information (e.g., where to look when in a task sequence). Especially today, with the rapid growth and incorporation of information technologies, advances in data fusion, automated diagnostics, and new reliance on condition-based (as opposed to calendar-based) approaches to equipment troubleshooting and maintenance, it is vital that information displays be redesigned from a user-centered approach to organizing information. …

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