designing appliances for older persons-老年人(4)

老年人设计

familiar technology. While this may assist their inter-action with the new device, it may constrain the dis-covery of new functionality not represented in the model. Familiar mental models may also interfere with developing appropriate mental models or inter-action behavior: for example, a typewriter model may interfere with the formation of a word-processing model that includes global find and re-place and the application of font and paragraph styles. When learning to use a new appliance, users may refine their understanding through a trial-and-error exploration of the controls. The discovery process is enhanced if they can relate the product to a familiar mental model of a similar or related product [5,9]. Successful formation and use of mental models depends on persons holding and working with infor-mation stored in memory [10]. Once formed in long-term memory, mental models of the functional opera-tion of an appliance may tend to remain static and resistant to alteration until changes to the functional-ity of the represented system in the real world re-quires information to be reprocessed in working memory [22]. Clearly, persons with MCI are at a disadvantage.

Learned behavior from previous technologies may have negative as well as positive consequences. Us-ers may anticipate control structures that create cog-nitive barriers that restrain seniors exploring new functionality [17]. If users can control basic product functions, they may ignore new functions and fea-tures, as their learning requires time and effort. The consequence: an undeveloped mental model of such cognitive tunneling is; the cost: partial use of the product. Moreover, reliance on an inadequate mental model—for example, a model of typewriting used in word processing—may generate a feeling of incapa-bility and a fear of doing something “wrong”.

5.Designing appliances for ageing

Product designers rarely overtly consider the needs of seniors when designing appliances. Those design-ers that do so, tend to rely on accessibility guidelines or commonly held presumptions of the needs and limitations of users. To counter unscientific ap-proaches to design, Pak and McLaughlin published a book on designing displays for older adults, with the intention to move designers from compliance with accessibility guidelines to evidence-based research [18

]. They focus on the effects of changes in percep-tion, cognition and movement with age.

The creation of domestic appliances that are usable by older persons requires a firm scientific foundation. Factors affecting design listed in the literature for human factors, cognitive psychology and psycho-physiology are:

D ecline in visual search and selective attention

[20]

Decline in recognizing targets due to decrease in

the ability to extract and integrate features in display objects [25]

Decline in ability disengage their attention from

current activity and redirect it to other display items [21]

Endurance of lexical and numerical abilities [7,13]

Impaired attention affects how many items a per-son can attend in a display. For example, an older adult seeking the fast-forward button on a D VD player focuses on a suitable target and the number of other items attended in the visual field decreases. This decrease, coupled with an age-related increase in latency of ocular movement affects performance in searching for a specific control in a busy display [26]. To reduce demands on attention, designers should therefore limit the number of perceptual features that users must integrate to discern targets from non-targets [25]. When designing technology for seniors, the lesson for appliance design is to make control and display items clearly different to both one another and the background by lessening shared features. Considering this in the design process may support deeper encoding, thereby making the target selection process more efficient over a shorter period. See Higgins for a discussion on the semantics of visual representations at the interface [8].

Two characteristics of cognitive decline seem par-adoxical: difficulty in switching between tasks and easy distraction. To compensate for fixation on the immediate task in situations where users perform multiple tasks contemporaneously (e.g., kitchens), appliances can be designed in a way that accentuates signals from displays based on those cognitive abili-ties that remain stronger across the lifespan. Different sensory modalities can also be used for competing information streams. In regard to distractions, task-irrelevant information can be removed to minimize clutter from signals that are irrelevant to the current task and likely subsequent tasks [25].

P.G. Higgins and A. Glasgow / Development of Guidelines for Designing Appliances for Older Persons 336