Is atypical rhythm a risk factor for developmental speech and language disorders?

Abstract

Although a growing literature points to substantial variation in speech/language abilities related to individual differences in musical abilities, mainstream models of communication sciences and disorders have not yet incorporated these individual differences into childhood speech/language development. This article reviews three sources of evidence in a comprehensive body of research aligning with three main themes: (a) associations between musical rhythm and speech/language processing, (b) musical rhythm in children with developmental speech/language disorders and common comorbid attentional and motor disorders, and (c) individual differences in mechanisms underlying rhythm processing in infants and their relationship with later speech/language development. In light of converging evidence on associations between musical rhythm and speech/language processing, we propose the Atypical Rhythm Risk Hypothesis, which posits that individuals with atypical rhythm are at higher risk for developmental speech/language disorders. The hypothesis is framed within the larger epidemiological literature in which recent methodological advances allow for large-scale testing of shared underlying biology across clinically distinct disorders. A series of predictions for future work testing the Atypical Rhythm Risk Hypothesis are outlined. We suggest that if a significant body of evidence is found to support this hypothesis, we can envision new risk factor models that incorporate atypical rhythm to predict the risk of developing speech/language disorders. Given the high prevalence of speech/language disorders in the population and the negative long-term social and economic consequences of gaps in identifying children at-risk, these new lines of research could potentially positively impact access to early identification and treatment. This article is categorized under: Linguistics > Language in Mind and Brain Neuroscience > Development Linguistics > Language Acquisition.

Keywords: developmental language disorder; dyslexia; rhythm; risk factor; specific language impairment.

Figure 1

Shared underlying mechanisms for musical rhythm and speech/language processing. (a) Models of underlying mechanisms for musical rhythm and speech/language processing emphasize the role of fine‐grained auditory processing, oscillatory brain networks and sensorimotor coupling (Fiveash et al., submitted). (b) Another line of literature emphasizes the shared role of processing of hierarchical structures in both musical rhythm and syntactic processing (e.g., Fitch & Martins, ; bottom figure is adapted from Heard & Lee, 2020)

Figure 2

Rhythm production ability and early literacy skills. Convergent evidence across data acquired with various methods, in support of associations between rhythm skills and language in preschool‐aged children (Reprinted with permission from Woodruff Carr, White‐Schwoch, Tierney, Strait, and Kraus (2014)). Children that performed well on a musical beat synchronization task (here called synchronizers, in red, shown on the rose plots on left to have better drumming accuracy) encoded speech more efficiently (top right) and show significantly better phonological awareness than their non‐synchronizer peers (bottom right). Synchronizers also performed better on a sentence repetition task (it is important to note that sentence repetition/imitation tasks not only require auditory perception and short‐term memory but also reflect deeper access to the grammatical structure of language: see Klem et al., 2015)

Figure 3

Rhythm perception and production difficulties in children with stuttering. (a) Children who stutter show impaired rhythm perception performance compared to TD children on a task requiring discrimination of simple and complex musical rhythmic sequences (Wieland et al., 2015). (b) Children and adolescents who stutter are less accurate than TD peers on synchronization tests, both tapping to a metronome at certain rates and tapping to the beat in music (Falk et al., 2015). Both figures are reprinted with permission from the original papers

Figure 4

Pleiotropy scenarios for shared versus separate genetic architecture of rhythm and speech/language. The Atypical Rhythm Risk hypothesis predicts that associations between rhythm and speech/language are (a) in part driven by genetic pleiotropy, such that a common set of causal genes affects both phenotypes directly, or (b) mediated genetic pleiotropy, such that genes directly affect rhythm phenotypes, and those phenotypes in turn affect individual differences in acquisition of speech/language during development, or (c) genes directly affect speech/language phenotypes, and those phenotypes affect individual differences in rhythm development. These models should be tested against the null hypothesis of separate genetic architecture. Moreover, a key to understanding the dynamics between genes, brain and behavior will be to test mediating neural endophenotypes linked to (d) shared or (e) separate genetic architecture