Searching information with a natural language dialogue system: a comparison of spoken vs. written modalities

This paper examines the effects of spoken vs. written dialogue modalities on the effectiveness of information search with a computerized retrieval system. Forty-eight adults familiar with the use of computers were asked to carry out six information retrieval tasks, engaging with the system using either spoken or written communication. The written modality was more efficient with regard to the number of dialogue turns, length of interaction with the system and mental workload. Even though the turns lasted longer in the written mode, they appeared to yield less mental workload. Moreover, spoken and written dialogues did not differ as regards the use of pronouns and articles. The implications for the development of natural-language dialogue systems are discussed.