Aphasia, phonological and phonetic voicing within the consonantal system: preservation of phonological oppositions and compensatory strategies

Abstract

A great number of studies in aphasiology have reported devoicing of voiced consonants in patients who have particular difficulty with the phonetic processing of speech. Recently, other studies have made attempts to account for these difficulties not only in negative terms of ‘deficit’ but also, positively, as a palliative strategy which patients would resort to in order to compensate, at least partly, for their deficit.The aim of this chapter is to contribute to the ongoing debate about devoicing phenomena in aphasia. We carried out a multiple-case study in which we acoustically analysed consonants distinguished by the voiced–voiceless contrast in order to determine, for each patient: (a) the nature of their deficit: whether it is phonological (pre-motor level of speech processing) or phonetic (motor level); and (b) the existence of possible palliative strategies. Results obtained from anarthria and Broca’s aphasia speech output indicate that the subjects differ in a statistically significant way (p<.05) between the VOT values according to whether the target consonant is voiced or voiceless. This can be interpreted, in the patients under study, as a deficit at the level of planning and/or implementation of the voicing feature without impairment, at a deeper level of processing, of the phonological encoding. These results also show that the subjects resort to alternative acoustic cues such as (i) Voice Termination Time (VTT), (ii) total duration of the segment, (iii) number of noise bursts or (iv) duration of the preceding vowel to mark the phonological opposition of voicing, therefore suggesting that they are making use of palliative strategies to compensate for their deficit.