Top/Bottom approaches
Using Benktzon's user pyramid (opposite) as a model of the spread of capabilities across the population, one of the most fundamental questions facing a designer when considering how best to design inclusively is that of which approach to adopt:
An issue that frequently affects the success of products developed using top-down approaches is the perception that they are 'medical' devices. Many were designed to meet a specific 'medical' need, and were often purchased by health authorities, for whom aesthetic value was a low priority compared to functionality and longevity.
For products developed using the top-down approach it is essential that they are designed to appeal to the largest possible audience if they are to have any chance of succeeding commercially. Perhaps the most straightforward way to broaden the appeal of a top-down product is to consider the widest possible range of users at the very outset of the design process. It may be more useful to consider the design problem at the highest level possible (e.g. difficulty moving an arm), rather than developing for a specific medical condition (e.g. cerebral palsy) or a particular symptom (e.g. tremor). Having identified the highest level description, the designers can then consider the initial target user group as a particular example of the range of users who may be able to ultimately use the product.
Consumers and manufacturers can both benefit from the broadening of the market base. Products that have been accepted by the mainstream market cannot, by definition, be stigmatising. Economies of scale make for cheaper products, as well as increased profits.