Subjective and objective evaluation of two types of dialogues in a call assistance service

Menu-based or system driven dialogues are widely used in interfaces to telephone services. The communication structure they impose on the customer differs from human-human dialogues, where control and initiative can switch from one partner to the other. It has often been claimed that mixed initiative dialogues could improve the user friendliness and efficiency of spoken language interfaces. In this paper we investigate whether mixed initiative dialogues do indeed outperform system driven dialogues as interface to a relatively simple service, i.e. a call assistance service that gives access to a small number of companies and agencies through a single premium rate access number. Results show that mixed initiative dialogues are not faster, nor more comfortable than system driven dialogues, at least in this service. We discuss possible explanations for our findings.