ABSTRACT
In Chapter 12 on usability testing under time-pressure, Kahmann and Henze make the point that, while rapid trialling techniques are necessary in industry, the comparison of different techniques and detailed observation is the domain of academe. In a design process, anticipation of future usage is enhanced by users' trialling with prototypes of the intended product, because the product is not yet available. These prototypes range from rough sketches to working prototypes. A prototype is defined by Ulrich and Eppinger (1995) as 'an approximation of the product along one or more dimensions of interest'. Kaulio (1997) asserts that this definition of a prototype is used by researchers and includes all types of representations of the product during development. In our research we have adopted this broad definition. The research focuses on users' trialling with prototypes. One question to be answered is which differences and resemblances there are between the use of a product, and derived design models, in terms of perception, cognition and use actions. The origins of observed differences can then be investigated, leading to proposals for how to execute users' trials during design processes, and how to construct prototypes for users' trialling as a design tool. Although one usually wants to represent a high level of detail of the design in a prototype, limited time and cost often prevents this from happening. Certain aspects of the design will not be realised in the prototypes, with possible consequences for the generalisability of the results from users' trials with these prototypes to usage of the intended product. A series of experiments has been planned to attempt to gain insight into these matters, and one of the early experiments is discussed in this chapter, leading to suggestions for the improvement of users' trialling with prototypes.
