Interfaces for speech recognition systems: the impact of vocabulary constraints and syntax on performance

An experiment was conducted to investigate the effects of vocabulary constraints and syntax on human interactions with a speech interactive system. Three dialogue styles for a telephone banking application, all using constrained vocabularies, were compared: yes/no, menu and query prompts. These styles differ both in the degree of vocabulary constraint, and in how that constraint i s communicated to the user. It was found that although i t involved more dialogue steps the yes/no interaction style was the most effective in terms of both task completion rates and performance time. The query strategy was least preferred by users.