The input processing, cognitive linguistic and oro-motor skills of children with speech difficulty

Children with speech difficulty of no known etiology are a heterogeneous group. While speech errors are often attributed to auditory processing or oro-motor skill, an alternative proposal is a cognitive-linguistic processing difficulty. Research studies most often focus on only one of these aspects of the speech processing chain. This study investigated abilities in all three domains in children with speech difficulty (n = 78) and matched controls (n = 87). It was hypothesized that groups of children with speech difficulty would perform less well than controls on all tasks, but that the proportion of children with speech difficulty performing within the normal range would differ across tasks. The input processing task required children to perceive the auditory-visual illusion in speech perception, where listeners perceive [da] when they hear [ba] presented in synchrony with the lip movements for [ga]. Diadochokinetic, isolated and sequenced movements tasks assessed oro-motor skills. Two non-verbal tasks evaluated rule derivation. The results indicated that rule derivation best discriminated typically developing and speech difficulty groups. Few children were identified as having an input or output difficulty, whereas difficulties with rule-derivation were common. The data support the notion that speech difficulty is, most often, associated with a central processing difficulty.