Complexity in articulatory and segmental levels of production

Precision of phonological errors in aphasia supports resource models of phonological working memory in language production

Working memory (WM) is critical for many cognitive functions including language production. A key feature of WM is its capacity limitation. Two models have been proposed to account for such capacity limitation: slot models and resource models. In recent years, resource models have found support in both visual and auditory perception, but do they also extend to production? We investigate this by analyzing sublexical errors from four individuals with aphasia. Using tools from computational linguistics, we first define the concept of "precision" of sublexical errors. We then demonstrate that such precision decreases with increased working memory load, i.e., word length, as predicted by resource models. Finally, we rule out alternative accounts of this effect, such as articulatory simplification. These data provide the first evidence for the applicability of the resource model to production and further point to the generalizability of this account as a model of resource division in WM.

Phonological complexity in intervention for Spanish-speaking children with speech sound disorder

The efficiency of intervention for children with speech sound disorder may be influenced by linguistic complexity of the phonological intervention target. Complex targets, particularly, later-acquired, less-known consonants and consonant clusters, have been linked to greater post-intervention generalization to untargeted phonological structures. Yet there is little direct evidence to support target selection based on linguistic complexity for Spanish-speaking children with speech sound disorder. This intervention study utilizes an experimental single-case design to examine the efficacy of intervention in Spanish using different complex targets (i.e. /ɡɾ/, /bɾ/, and /l/). For each of the four Spanish-speaking children with speech sound disorder, sounds at 0% accuracy during baseline were monitored across the baseline period, during and post-intervention, and at one- and two-month follow-up visits. Over the course of intervention, only one participant achieved mastery of the targeted structure in practiced words. However, all participants demonstrated some amount of broad phonological generalization to untargeted consonants or clusters. Variable learning trajectories and broad phonological generalization are discussed as they relate to participant characteristics and linguistic complexity.

Apraxia of speech and the study of speech production impairments: Can we avoid further confusion? Reply to Romani (2021)

We agree with Cristina Romani (CR) about reducing confusion and agree that the issues raised in her commentary are central to the study of apraxia of speech (AOS). However, CR critiques our approach from the perspective of basic cognitive neuropsychology. This is confusing and misleading because, contrary to CR's claim, we did not attempt to inform models of typical speech production. Instead, we relied on such models to study the impairment in the clinical category of AOS (translational cognitive neuropsychology). Thus, the approach along with the underlying assumptions is different. This response aims to clarify these assumptions, broaden the discussion regarding the methodological approach, and address CR's concerns. We argue that our approach is well-suited to meet the goals of our recent studies and is commensurate with the current state of the science of AOS. Ultimately, a plurality of approaches is needed to understand a phenomenon as complex as AOS.