This paper reports on research involving a series of large-scale field experiments using a new Wizard of Oz (WOZ) system for the investigation of users' attitudes towards automated telephone services. The paper focuses on the identification of a service's usability attributes, those features and characteristics of a system which influence the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in a particular environment. The attributes which are found to be most salient are used to form the content of a questionnaire designed to measure attitudes towards usability of automated telephone services. Experimental results derived by using such a questionnaire are discussed.

Keywords: usability attributes, automated telephone services, speech interfaces, Wizard of Oz, questionnaires.