How do persons with apraxia of speech deal with morphological stress in Spanish? A preliminary study

Equal stress across adjacent syllables and extended syllable durations are amongst the most salient features of acquired Apraxia of Speech (AOS). Most studies conclude that there is a deficit in durational cue processing, whereas the other acoustic stress correlates remain relatively unimpaired. Spanish is a free-stress language in which stress patterns are contrastive, especially in verbal forms (e.g. lavo /'labo/ '[I] wash' vs lavó /la'bo/ '[He/she] washed'). The aim of this preliminary study is to determine whether persons with AOS are able to make the intended stress pattern identifiable and, if so, to determine which acoustic cues they use to avoid the 'equal stress' phenomenon. The results show that, for each parameter considered (duration, intensity, fundamental frequency), apraxic participants' productions differed from those of controls to varying degrees depending on the task. However, 91.7% of the apraxic participants' realisations were perceived as corresponding to the intended tense and person. These results are interpreted as deriving from a motoric deficit affecting morphological stress processing by subjects with AOS combined with an idiosyncratic compensatory use of the stress cues in order to avoid 'equal stress'.