Motor Behaviors and Associations with Later Consonant Inventory in Nonverbal Children with ASD

Background: Motor impairments are often present in individuals with ASDs and can appear early, even before core features are identifiable (e.g., Bryson et al., 2007, Minshew et al., 2004).  Further, some specific motor impairments are related to core features. Regarding communication, poorer imitation skills are negatively associated with severity of more severely impaired social and communicative skills  (Dawson & Adams, 1984; Zachor et al., 2010) and oromotor skills are concurrently and longitudinally associated with speech intelligibility (Gernsbacher et al., 2008).

In typical children and children with developmental delay, consonant production during prelinguistic development predicts later developing oral communication (e.g., Stoel-Gammon, 1989; McCathren et al., 1999).  At nine months, consonant inventory differentiates infants who are at high-risk and low-risk for developing ASD (Paul et al., 2011). Although many children with ASDs develop oral communication, roughly 30% remain nonverbal into their school years (Lord et al., 2006), and failure to develop oral communication drastically impacts nearly all aspects of life.

 Objectives: 1.  To determine associations between (a) manual motor imitation, (b) basic oromotor skills (i.e., eating), and (c) oromotor imitation.  2.  To determine the extent to which early motor variables predict later consonant inventory in young nonverbal children with ASD. 

Methods: This study is part of a larger research project aimed at determining factors that influence the development of useful language in children with ASDs.  Participants have a diagnosis of an ASD and are assessed five times at four-month intervals.  All children are nonverbal at Time 1 (T1) as determined by the production of five or fewer words during all T1 assessments combined.  Available T1 and Time 3 (T3) motor and consonant inventory data were used for this study. T1 N=50, CA: M=35.9, SD=7.8. Time 3 (T3) N=32, CA: M=44.7, SD=7.5.  Motor variables at T1 & T3 were: (a) Motor Imitation Scale (MIS), assessing manual motor skills (Stone et al., 1997), (b) oromotor imitation, and (c) eating.  Consonant inventory scores were drawn from the Communication and Symbolic Behavior Scales (Wetherby & Prizant, 2002).

Results: (1) Associations between motor behaviors: significant associations were present between basic oromotor skills and oromotor imitation, and between oromotor imitation and manual motor imitation. (2) Associations between early motor behaviors and later consonant inventory: linear regression analysis revealed that oromotor imitation was a highly significant predictor of consonant inventory eight months later (β= .53, p=.006). Manual motor imitation approached significance (p=.051) and eating was not significant in predicting consonant inventory.

Conclusions: Both manual motor imitation and eating skills are associated with oromotor imitation but only oromotor imitation significantly predicts later consonant inventory. Therefore, oral motor imitation is potentially a more important skill to address in early language interventions. Oromotor imitation may be tapping basic motor skills, praxis and perhaps attention and sensory responsiveness, but further research is needed to understand the extent to which each factor is present.