Effects of Recognition Accuracy and Vocabulary Size of a Speech Recognition System on Task Performance and User Acceptance

Abstract

The purpose of this study was to determine the effects of recognizer accuracy and vocabulary size on performance of a speech recognition system. Subjects ranging in age from 20 to 55 years performed a data-entry task using a simulated speech recognizer that simulated three accuracy levels and three levels of available vocabulary. The accuracy level at which the recognizer was performing significantly influenced the time to complete the task as well as the user's acceptability ratings but had only a small effect on the number of errors left uncorrected. Available word-level vocabulary size also significantly affected the task completion time; however, its effect on the average number of uncorrected errors and on the acceptability ratings was negligible. Age of the subject was found to influence both objective and subjective measures. Older subjects required more time to complete the tasks, though they consistently rated the speech input systems more favorably than did the younger subjects. Minimal experience with computer text editors may account in part for the speed differences between older and younger subjects.