Effects of displayless navigational interfaces on user prosodics

Displayless interface technology provides speech-based access to computer applications for which visual access is not possible. These applications are increasingly prevalent, especially in situations requiring mobility, such as navigational applications. To ensure the successful deployment of this technology however, many human factors issues must be addressed. In particular, its nonvisual nature requires verbal presentation of spatial data. Prosodics, or nonverbal aspects, of human speech have been established as an indicator of cognitive stress. In this paper, we examine the assumption that the cognitive burden placed on the user by displayless access to spatial data would significantly alter the prosodics of the user’s speech. Results were gathered through experiments in which user interactions with a prototype speechbased navigational system were recorded, post-processed, and analyzed for prosodic content. Subjects participated in two sessions, one using a speech-based, displayless interface, and a second using a multimodal interface that included a visual-tactile map display. Results showed strong evidence of significant changes in subjects’ prosodic features when using a displayless versus a multimodal navigational interface for all categories of subjects. Insights gained from this work can be used to improve the design of the user interface for such applications in addition to improving the underlying prosodic pattern detection algorithms.