Grammatical morphology and perception of synthetic and natural speech in children with specific language impairments

Studies investigating the relationship between the use of inflectional morphology and speech-perception abilities in children with SLI traditionally have employed synthetic speech stimuli. The purpose of this study was to replicate the findings reported in Leonard, McGregor, and Allen (1992) with an older group of children with SLI and to determine if the pattern of deficits seen for synthetic speech extends to perception of natural speech stimuli. The speech-perception abilities of 27 children between the ages of 6;11 and 8;11 (15 SLI and 12 NL) were compared using natural and synthetic versions of the [das]-[daS], [dabiba]-[dabuba], and [i]-[u] contrast pairs originally used in Leonard et al. The findings reported by Leonard et al. were replicated with synthetic speech but not for the natural speech. Use of inflectional morphology in obligatory contexts by the children with SLI was not significantly correlated with their perception abilities for any of the natural or synthetic speech-contrast pairs. Further, although both groups' ability to maintain the target contrast in memory declined over the span of the trials for all target contrasts for both natural and synthetic speech, the rate of decline did not differ significantly between the SLI and NL groups. Findings are discussed with respect to possible deficits in linking phonological representations to grammatical representations in children with SLI.