Abstract
This paper analyses the factors that predict substitution errors produced by four Broca’s and four conduction aphasic subjects, all native speakers of Spanish, in reading and repetition tasks. Errors were elicited using a list of words where type of consonant, lexical stress and phonetic context were controlled for and where variables related to frequency of occurrence (word and syllable) and phonological neighbourhood characteristics were assigned using available online corpora. 675 substitution errors were obtained and preferential tendencies to devoice, occlusivise or spirantise were identified. Logistic regression mixed-effect models were performed on these three types of substitution errors to identify the predictors depending on the aphasic profile. While our results lent support to the hypothesis of a concomitant phonetic deficit in fluent aphasia, contrary to the classical claim, it also revealed differential patterns in the phonic behaviour of patients regarding the access to mental syllabary or syllabic position effects. Our results are discussed in relation to the phonetic vs. phonological impairments dimension in aphasia and the seriality/ interactivity axis in speech architectures.
Highlights
Speech production models guiding research in the field of acquired speech impairments are anchored in contrasting viewpoints about the nature of language and mechanisms involved in speech production and its impairments
The word-form encoding proceeds according to the principle of seriality, dominant in this account, which postulates that only one item selected during the phonological encoding can constitute the entry of the phonetic module, where it is further translated into motor commands
The goal of the analyses reported in the preceding paragraphs was to identify factors predicting three different kinds of substitution errors—devoicing, occlusivisation and spirantisation—observed in the aphasic speech output
Summary
Speech production models guiding research in the field of acquired speech impairments are anchored in contrasting viewpoints about the nature of language and mechanisms involved in speech production and its impairments. One such viewpoint holds that language is composed of relatively autonomous processing subsystems where each of them is assigned a specific functional role such as lexical or morphological processing. In this account, speech production is conceptualised as a linear top-down process combining retrieval of information stored in the memory and computation processes involving units of encoding specific to a given domain. A shortcoming of such architectures, with respect to phonetic and phonological processing, consists in the fact that it does not account for the variability which is systematically revealed during the conversion of higher level representations into overt speech
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