The Development of Multimodal Communication In Infants at High Risk for Autism Spectrum Disorders

Background: The ability to coordinate communicative expressions from different behavioral modalities (e.g., vocal, gestural) is a crucial component of communication (e.g., Crais et al., 2009). In addition to impairments in gesture, pre-verbal speech sounds, and expressive language, children with autism spectrum disorders (ASD) have difficulty producing these behaviors in coordination (e.g, Stone et al., 1997). This study compared the development of multimodal communication in infants at heightened ASD risk (later-born siblings of children with autism; HR) to that of infants with low ASD risk (infants with a negative family history of ASD; LR) to determine whether HR infants demonstrate communicative coordination delays and whether such impairments are related to a later ASD diagnosis.

Objectives: To investigate developmental trajectories in the production and temporal coordination of communicative behaviors from 8 to 18 months in HR and LR infants.

Methods:  Forty-seven HR infants (43% male) and 29 LR infants (45% male) were observed at home for 30 minutes during everyday household activities and play with a primary caregiver. The 8, 10, 12, 14, and 18 month observations were coded for communicative gestures, words, and non-word vocalizations produced by the infant. Coordinated bouts of communicative behaviors (i.e., instances in which gestures overlapped in time with non-word vocalizations or words) were identified. At 36 months, HR infants were administered the ADOS-G (Lord et al., 2000); to date, six infants have received an ASD diagnosis (HR-ASD). The remaining HR and LR infants did not meet ASD criteria (No Diagnosis; HR-ND, LR-ND).

Results: Preliminary analyses were conducted using Hierarchical Linear Models (Bryk & Raudenbush, 1992). Unconditional and conditional growth models were estimated separately for Overall Communicativeness (the total number of all gestures and vocalizations produced in a given session) and Coordinated Bouts (the total number of all gesture-vocalization coordinations). A one parameter (slope only) linear model adequately represented the individual growth data collected in this study. After controlling for gender, Overall Communicativeness growth trajectories for the LR-ND, HR-ND, and HR-ASD groups were positive (increasing) but not significantly different from one another. However, relative to the LR-ND group, Coordinated Bouts grew at a slower rate (i.e., .79 bouts slower per month) in the HR-ND group (p = .028). This pattern was more pronounced for the HR-ASD infants, who, on average, gained 1.60 bouts fewer per month than LR-ND infants (p = .000). Over time, this slower growth rate translated into progressively larger standard deviation differences between the LR-ND and HR-ASD groups. At 12 months, scores for the HR-ASD infants fell on average 10.53 SD below those for LR-ND infants, but by 18 months the difference had more than doubled, with HR-ASD infants scoring 26.32 SD below LR-ND infants.

Conclusions: There is a broad pattern of delay in the production of temporally coordinated communicative behaviors among HR infants that cannot be simply attributed to a delay in the overall production of communicative acts. This delay appears to be more pronounced in HR infants who eventually receive an ASD diagnosis, suggesting that multimodal communication may be an early behavioral marker of ASD.