Conspiring simplification strategies of [Obstruent+Liquid] clusters in a case study of child Greek: emergence of the marked

This paper addresses the idiosyncratic cluster simplification patterns observed in a child with disordered phonological development, who is acquiring Greek. The child has mastered word-internal and word-final codas and clusters of reversed sonority. However, the child does not realise the target well-formed tautosyllabic [Obstruent+Liquid] clusters with rising sonority. The child's system requires a single onset with maximum sonority dispersion between the onset and the syllable nucleus. As a result, cluster simplification occurs, via reduction to the less sonorous Obstruent - the most prevalent reduction pattern cross-linguistically. However, at the same time, the grammar requires faithful realisation of the target segment number. This requirement is fulfiled through two distinct conspiring metathesis patterns, distributed complementarily, resulting in the realisation of marked structures. The patterns depend on the position of the cluster within the target word. In word internal position, a compensatory metathesis of the Liquid takes place in the preceding syllable coda. In word initial position, the Manner of Articulation of the metathesised Liquid is delinked, while its Coronal Place of Articulation is faithfully preserved, and is realised by default as a Coronal Sibilant [s]. The latter Sibilant is attached as an appendix to the syllable node at the word left-edge. We argue that, in the grammar of this child, there is a-synchronisation between the development of the prosodic word layer and the development of syllable layer. Specifically, a-synchronisation is evident in the development of the (branching) onset syllabic subconstituent.

Disentangling Effects of Memory Storage and Inter-articulator Coordination on Generalization in Speech Motor Sequence Learning

Generalization in motor control is the extent to which motor learning affects movements in situations different than those in which it originally occurred. Recent data on orofacial speech movements indicates that motor sequence learning generalizes to novel syllable sequences containing phonotactically illegal, but previously practiced, consonant clusters. Practicing an entire syllable, however, results in even larger performance gains compared to practicing just its clusters. These patterns of generalization could reflect language-general changes in phonological memory storage and/or inter-articulator coordination during motor sequence learning. To disentangle these factors, we conducted two experiments in which talkers intensively practiced producing novel syllables containing illegal onset and coda clusters over two consecutive days. During the practice phases of both experiments, we observed that, through repetition, talkers gradually produced the syllables with fewer errors, indicative of learning. After learning, talkers were tested for generalization to single syllables (Experiment 1) or syllable pairs (Experiment 2) that overlapped to varying degrees with the practiced syllables. Across both experiments, we found that performance improvements from practicing syllables with illegal clusters partially generalized to novel syllables that contained those clusters, but performance was more error prone if the clusters occurred in a different syllable position (onset versus coda) as in practice, demonstrating that inter-articulator coordination is contextually sensitive. Furthermore, changing the position of a cluster was found to be more deleterious to motor performance during the production of the second syllables in syllable pairs, which required talkers to store more phonological material in memory prior to articulation, compared to single syllables. This interaction effect reveals a complex interplay between memory storage and inter-articulator coordination on generalization in speech motor sequence learning.

Correlation between the measure for cluster proximity (MCP) and the percentage of consonants correct (PCC)

A measure was recently proposed for the quantitative evaluation of consonant clusters in child developmental speech, the measure for cluster proximity (MCP). Its advantage over the widely used measure of the percentage of consonants correct (PCC) is that it differentiates the three main stages of cluster production: reduction, vowel epenthesis, and two-members, correct or not. The purpose of the present article is two-fold: a) to contrast MCP and PCC in two-member word-initial clusters produced within children with speech sound disorders (SSDs), tested before and after therapy, as well as in running speech within typically developing children, and b) to examine the correlation between the two measures across children in typical or atypical speech development. Data used are comprised of 34 sets with 18 word-initial cluster types, taken from the speech samples of 18 children. It is found that while there are generally large deviations between the two measures in individual clusters within and between children, the measures have a strong and statistically significant correlation when averaged over all clusters per child, or over all children per cluster class based on the manner of articulation. For the data at hand, a linear equation is obtained yielding MCP values from PCC values with a high coefficient of determination. The results suggest that PCC norms that are used to assess consonants can be used to predict MCP norms in order to assess consonant clusters in child developmental speech.

Chunking of phonological units in speech sequencing

Efficient speech communication requires rapid, fluent production of phoneme sequences. To achieve this, our brains store frequently occurring subsequences as cohesive "chunks" that reduce phonological working memory load and improve motor performance. The current study used a motor-sequence learning paradigm in which the generalization of two performance gains (utterance duration and errors) from practicing novel phoneme sequences was used to infer the nature of these speech chunks. We found that performance improvements in duration from practicing syllables with non-native consonant clusters largely generalized to new syllables that contained those clusters. Practicing the whole syllable, however, resulted in larger performance gains in error rates compared to practicing just the consonant clusters. Collectively, these findings are consistent with theories of speech production that posit the consonant cluster as a fundamental unit of phonological working memory and speech sequencing as well as those positing the syllable as a fundamental unit of motor programming.

Patterns in German /ʃC/-cluster acquisition

This study reports on the developmental patterns of /ʃC/ clusters in 145 normally developing monolingual German-speaking children between 2;00 and 2;11. All children completed a picture naming task to allow a systematic qualitative analysis of the production patterns. Children's reductions of target /ʃC/clusters are examined and are evaluated with respect to two models, 'factorial typology' and 'headedness', to account for them. The results reveal expected patterns of C2 retention for '/ʃ/+[-continuant]' (e.g. '/ʃ/+stop' and '/ʃ/+nasal') targets, and a rather indeterminate pattern for /ʃl/ and /ʃʁ/. The results for /ʃv/, a clear-cut preference of C2 retention, were rather unexpected, as the C2 is a [+continuant]. The explanation offered for the retention of /v/ is related to a place constraint. The study also examines the data from children who reached an advanced stage of cluster formation with differential targets. More specifically, in several children, one target, /ʃv/, is found to have stayed behind in the reduction phase while all others have advanced to the 'cluster stage'. Neither the type nor the token frequencies seem satisfactory in accounting for the specific behaviour of /ʃv/. The explanation offered for the uniqueness of this target may be its non-abidence to the Sonority Sequencing Principle (SSP) because of its flat sonority and the Obligatory Contour Principle (OCP) [continuant], because of the unchanging 'continuance' which is demanded by the OCP. Theoretical and clinical implications are discussed.

Word-initial rhotic clusters in Spanish-speaking preschoolers in Chile and Granada, Spain

The current paper describes Spanish acquisition of rhotic onset clusters. Data are also provided on related singleton taps/trills and /l/ as a singleton and in clusters. Participants included 9 typically developing (TD) toddlers and 30 TD preschoolers in Chile, and 30 TD preschoolers and 29 with protracted phonological development (PPD) in Granada, Spain. Results showed age and developmental group effects. Preservation of cluster timing units preceded segmental accuracy, especially in stressed syllables. Tap clusters versus singleton trills were variable in order of mastery, some children mastering clusters first, and others, the trill. Rhotics were acquired later than /l/. In early development, mismatches (errors) involved primarily deletion of taps; where substitutions occurred, [j] frequently replaced tap. In later development, [l] more frequently replaced tap; where taps did occur, vowel epenthesis sometimes occurred. The data serve as a criterion reference database for onset cluster acquisition in Chilean and Granada Spanish.