Retrospective video analysis of the early speech sound development of infants and toddlers later diagnosed with lateralisation errors.

Purpose: Although lateralisation errors (LEs) are a common speech sound disorder, no studies have examined their early development. The purpose of this exploratory small-scale investigation was to compare the early (birth-24 months) speech sound development between children later diagnosed with LEs and typically developing children.Method: This was a between-group case-controlled design with six monolingual English-speaking participants. Participants were White, non-Hispanic girls with at least one college-educated parent. As children, three had been diagnosed with lateralisation speech sound errors and three demonstrated typical speech sound development. Participants' parents provided home video-recordings of the participants as infants/toddlers between birth and age 2. These videos were then analysed for the amount, type and diversity of sounds, and canonical babbling onset.Result: There was no statistically significant between-group difference in the volubility (i.e. combined frequency of non-resonant and resonant utterances) or in the age at which [s] or [z] emerged. However, infants/toddlers who were later diagnosed with LEs showed reduced frequency/minute in production of resonant utterances and consonants (including [s, z]), used fewer different consonants/minute, and used fewer syllable shapes/minute compared to typically developing infants/toddlers. At 7-12 months, none of the infants/toddlers later diagnosed with LEs, but all participants in the comparison group had reached the canonical babbling stage.Conclusion: Children who have LEs may have had a less robust speech sound system as infants/toddlers than their typically developing peers. However, these findings must be considered with caution due to the significant limitations of this investigation.