Temporal parameters of speech production in bilingual speakers with apraxic or phonemic paraphasic errors

Abstract

Background: The four‐level framework of speech production (Van der Merwe, 1997) suggests that language of production of a bilingual speaker can be viewed as a contextual factor increasing the complexity of speech production. A comparison of first‐ versus second‐language speech production in individuals with apraxia of speech or phonemic paraphasic speech errors may clarify the difference in the underlying disorders in these two populations. Aims: This study examined the effect of first‐ versus second‐language (L1 versus L2) speech production on specific temporal parameters of speech in bilingual normal speakers and bilingual speakers with either apraxic or phonemic paraphasic speech errors. The purpose was to determine if second‐language speech production will differentiate between normal speakers and speakers with speech‐level neurogenic disorders and between speakers with phonological planning or speech motor planning and programming disorders. Methods and Procedures: Three persons with apraxia of speech (AOS), three with phonemic paraphasias (PP), and five normal‐speaking participants were included in the study. Participants were required to read phonemically similar L1 and L2 CVC words in a two‐word carrier phrase, five times each, at a normal and fast speaking rate. Acoustic analysis of on‐target productions included vowel duration, utterance duration, utterance onset duration, and voice onset time. Data processing involved a descriptive approach using a measure of central tendency—the mean. Intra‐participant comparisons were made across contexts (L1, L2, fast speaking rate, and normal speaking rate). Outcomes and Results: Five participants with AOS and PP seemed to be influenced by speaking in L2 to a greater extent than the normal speakers and one participant with PP, in that they more frequently experienced difficulty with durational adjustments (decreasing duration in the fast speaking rate) in L2 than in L1. Furthermore, the participants with AOS or PP also exhibited a greater extent of durational adjustment in L1 than in L2. Conclusions: The results of this study suggest that L2 speech production is more challenging than speech production in L1 for participants with either AOS or PP. The current study could not differentiate between all speakers with a disorder in phonological planning and speakers with a motor planning and programming disorder. Individual patterns appear to exist in speakers with PP. Increased processing demands seem to impact on the phonological planning and the speech motor planning and programming levels of speech production.