ASD and FXS: Vocalization Differentiation in the First Year of Life

Background:  Prelinguistic behaviors are foundational for later language skills. The canonical babbling stage emerges around five months and marks the shift between prelinguistic skills to adult like speech (Oller, 2000) with a delay strongly suggesting a developmental disability (Oller et al. 1999; Stark et al. 1988; Stoel-Gammon 1989; Patten et al., 2014). Autism Spectrum Disorders (ASD) and Fragile X syndrome (FXS) are two neurodevelopmental disorders associated with language impairment. A recent retrospective study (Patten et al., 2014) reported infants later diagnosed ASD are delayed in achieving the canonical babbling stage and demonstrate reduced volubility (total syllables) in comparison to typically developing infants. However, no previous studies compare the early vocalization skills of infants with ASD to those of infants with other neurodevelopmental disabilities such as FXS. 

Objectives: The purpose of this study is to determine whether there are differences in the vocalization behaviors between infants with ASD and those with FXS-no ASD in the first year of life. This information has the potential to inform our understanding of the derailment in speech and language acquisition in the neurodevelopmental disorders. About 15-33% of children with FXS go on to have an ASD diagnosis, and previous studies have found the communicative functioning of children with FXS+ASD to be very similar to other children with ASD-only and different from children with FXS-no ASD (Klusek, Martin, & Losh, 2014). Thus, our focus in this study is to determine whether children with ASD-only can be differentiated from those with FXS-no ASD based on quantitative and qualitative features of their vocalizations.

Methods: Home videos of infants (9 - 12 months) later diagnosed with FXS-no ASD (CARS scores less than 30) are being analyzed to compare to the frequency of infant produced canonical babbles and noncanonical syllables produced by infants later diagnosed with ASD, or infants with typical development; comparable home videos for the ASD and typical samples were previously coded, with results reported in Patten et al. (2014). 

Results: Preliminary results from the study indicate 3/8 participants with FXS, 12/21 with ASD and 10/14 with TD having produced at least one canonical babble in a ten-minute video. Average syllables produced in 10 minutes was 51.5 for FXS, 79.8 for ASD, and 119 for TD. Recruitment for additional participants with FXS is ongoing. We expect to have at least 15 participants in five months.

Conclusions: Characteristics of canonical babbling and volubility may serve as markers to differentiate ASD from other neurodevelopmental disorders such as FXS-no ASD. These characteristics may also inform our understanding of the origins of speech and language impairment.