Effects of rate reduction on severe spastic dysarthria

By K.C. Hustad and K. Sassano

Rate reduction can be a powerful intervention strategy for improving intelligibility in speakers who have dysarthria. However, research efforts have largely overlooked the effects of rate reduction for speakers with severe-profound intelligibility problems, perhaps in part because speech rate is often significantly reduced for these individuals and further decreases in rate may seem counter-productive. The present study examined the effects of speaker-implemented interword pauses as a strategy for reducing rate in two individuals with severe spastic dysarthria secondary to cerebral palsy. Measures of intelligibility, speech rate, articulation rate, and pause frequency and duration were examined for three different rate conditions: habitual speech, speaker-implemented interword pauses, and experimentally lengthened interword pauses. Results showed an average increase in intelligibility of 20% across the two speakers for the speaker-implemented pause condition relative to habitual speech. Experimentally lengthened pauses did not further increase intelligibility. Preliminary rate measures suggest that increases in intelligibility associated with speaker-implemented interword pauses can be explained by both increased pause time and increased articulation time. Individual differences among speakers having the same habitual intelligibility scores and type/severity of dysarthria were observed and will be discussed relative to rate measures.