Speech Versus Touch: A Comparative Study of the Use of Speech and DTMF Keypad for Navigation

(speech vs. Dual Tone Multiple Frequency [DTMF]) in a phone-based message retrieval system. Unlike previous studies that compared these two modalities, the speech system used in this study was a fully functioning natural language system, and participants in this study were working professionals, rather than college students. Results indicate that (a) DTMF was more effective and efficient for linear tasks, whereas speech was better for nonlinear tasks; (b) speech was preferred to DTMF by a majority of users; (c)speechwasjudgedasbeingmoresatisfying,moreentertaining,andeasiertousethan DTMF; and (d) user preference for a particular modality was better predicted by user performance in nonlinear tasks rather than linear ones. Possible reasons for users ’ continuing preference for the speech modality even after experiencing fairly high recognition errors are discussed. Finally, the importance of examining speech user interfaces from other perspectives, in addition to efficiency maximization, is emphasized. The results of this study have theoretical, as well as practical, implications for the design of speech user interfaces and interactive voice response applications. 1.