Using critical path analysis to model multimodal human-computer interaction

In this paper, the concept of multimodal human-computer interaction is explored. It is proposed that multimodality can be de"ned from human or technology perspectives, which place emphasis on di!erent attributes of the system. Furthermore, in this paper it is argued that the most e!ective de"nition of multimodality concentrates on task and goal dependencies. Not only does this permit consideration over and above the technology/human distinction, but also allows consideration of multiple tasks. In order to explore this notion, critical path analysis is used to develop models of multimodal systems. The model describes multimodal HCI, and allows consideration of the e!ects of modality dependency. The models allow prediction of transaction time under various conditions. Predictions arising from these models are shown to be good "ts with data obtained from user trials. Thus, it is proposed that one can develop and evaluate preliminary versions of multimodal systems prior to prototype development. ( 2001 Academic Press