The social validity of script training related to the treatment of apraxia of speech

Abstract

Background: Social validity is an important yet under-examined aspect of treatment efficacy that determines how the effects of treatment are perceived by people other than the clinician/researcher. This is particularly true of treatments to improve the speech of adults with acquired neurogenic disorders. Aims: The purposes of this investigation were to evaluate the social validity of a modified script training treatment protocol, to explore how aspects of a client's speech correspond to varying rater judgements, and to determine which of the listener ratings were most predictive of ratings of overall quality. Methods & Procedures: A total of 124 young, naïve listeners were asked to rate the quality of speech of an 81-year-old woman with moderate–severe apraxia of speech during utterances with varying levels of script correctness (low, medium, high), number of errors (low, high), and rate (slow, faster). Judgements were made on the understandability, ease of production, naturalness, and overall quality of speech. Outcomes & Results: All main effects and interactions were statistically significant. As script correctness, speaking rate, and number of errors increased, listener ratings were significantly more favourable. Interactions demonstrated increasing correctness, error, and rate with significantly more favourable listener ratings. The listener ratings that predicted improved perceptions of overall quality, weighted highest to lowest, were: understandability, naturalness, and ease of production. Error types were analysed and revealed that phrase repetitions appeared to be perceived positively and that unintelligible words and interjections appeared to be perceived negatively. Conclusions: The modified script training protocol applied to a woman with marked apraxia of speech appeared to be socially valid with these naïve raters. Listeners appeared to be sensitive to the amount and the quality of speech output generated by the speaker. Listeners appeared to perceive struggle behaviours as negative, increased speech output (including repetitions and empty speech) as positive, faster speech (closer to a normal speaker's average word per minute) as preferable to slow speech, and more understandable speech and more natural speech as better quality speech. Based on these data, the accuracy and fluency of script production are important treatment goals.