The design of speech-based automated mobile phone services using interface metaphors
Interface metaphor is a widely used design technique for interactive computer systems. The advantages of using interface metaphors derive from their ability to promote active learning, which enables a user to transfer knowledge from a familiar real world domain, to an unfamiliar computing domain. Interface metaphor is not currently used for the design of automated phone services, and it was the aim of this thesis to examine whether interface metaphor could improve the usability of speech-activated automated mobile phone services. A human-centred design methodology was followed to generate, select, and develop potential metaphors, which were used to implement metaphor-based phone services. An experimental methodology was then used to compare the usability of the metaphor-based services with the usability of currently available number-based phone services. The first experiment examined the effect of three different interface metaphors on the usability of a mobile city guide service. Usability was measured as a range of performance and attitude measures, and was supplemented by telephone interview data. After three consecutive days of usage, participants both preferred, and performed better with, the service that was based on an office filing system metaphor. Experiment two was conducted over a six week period, and investigated the effect of users' individual differences, and the context of use, on the usability of both the office filing system metaphor-based service, and a non-metaphor service. The results showed that performance with the metaphor-based service was significantly better than performance with the non-metaphor service. The usability of the metaphor-based service was not significantly affected by users' individual characteristics and aptitudes, whereas the number-based service was, suggesting that metaphor-based services may be more usable for a wider range of potential users. Usability levels for both services were found to be consistent across both private and public locations of use, suggesting that speech-activated mobile phone services provide a flexible means of information access. Experiment three investigated the strategies used by participants when interacting with mobile phone services, specifically the visualisation strategy that was used by two thirds of the metaphor-based service participants in experiment two. In addition to the attitude and performance measures used for experiments one and two, face-to face interviews were conducted with participants. The results indicated that significantly more participants visualised the metaphor-based services relative to a non-metaphor service, and that visualisation of the service structure led to significant performance improvements. This thesis has demonstrated the usability benefits of interface metaphor as a design technique for speech-based mobile phone services. These benefits of metaphor appear to derive from their ability to provide a mental model of the phone service that can be visualised, and their ability to accommodate the individual differences of users.