The Truncation of Prompts in Phone Based Interfaces: Using Tott in Evaluations

Abstract

The Intelligent Interfaces Group at NYNEX Science and Technology has evaluated numerous phone based interfaces (PBIs) during the course of iterative design. Many of the PBIs studied allow users to truncate spoken prompts by pressing keys on their touch-tone telephones. We have found that mistaken assumptions about how and when users will truncate spoken prompts may lead to large discrepancies between the expectations of system designers and the behavior of users. In order to study truncation behavior, we created the Task Oriented Taxonomy of Truncation (TOTT). This taxonomy can be used to describe the behavior of users in truncating spoken prompts in PBIs. TOTT was found to facilitate our understanding of users' truncation behavior and allowed us to change the PBI prompts to better fit this behavior. We found that many users did not interrupt the spoken prompts and we speculate that they may be using a model of turn-taking from human conversation. Future areas of research and applications of TOTT are discussed.