Effects of Speech Intelligibility, Morphological Confusions, and Redundancy on Task Performance

Abstract

Speech is a vital means of communication for completing many tasks. The speech intelligibility needed for successful communication may be degraded by ambient noise levels, poor communication equipment, or hearing impairments. The present research tested the impact of speech message content on task performance under conditions of degraded speech intelligibility. Sixteen subjects participated in a laboratory experiment using on a board game. Message redundancy, morphological confusions, and speech intelligibility were varied. Task performance and subjective workload were measured. Morphological confusions adversely affected performance (both speed and accuracy) and subjective workload (SWAT) to an increasingly greater extent as speech intelligibility decreased. High redundancy improved the accuracy of performance and subjective workload when speech intelligibility decreased; however, high redundant messages were longer and required more time to process than low redundant messages. These results extend earlier work which measured the impact of morphological confusions and redundancy on speech intelligibility itself to the measurement of their impact on performance. Implications for the development of message content guidelines and their impact on performance are discussed.