Diagnosing inconsistent phonological disorder: quantitative and qualitative measures.

Studies of children's consistency of word production allow identification of speech sound disorder. Inconsistent errors are reported for two groups of children: childhood apraxia of speech (CAS) due to difficulty with the motoric precision and consistency of speech movements; and inconsistent phonological disorder (IPD) attributed to impaired phonological planning. This paper describes the inconsistent productions of children with IPD in comparison to typically developing children. In two studies of suspected SSD (N = 135), 22 children pronounced ≥40% of 25 words inconsistently on three repeated trials. No participant had symptoms of CAS. They were monolingual and spoke Australian- or Irish-English. Assessment determined the proportions of words said consistently (i.e. the same across productions: all correct or with the same error) or inconsistently (i.e. differently across productions: at least one correct and one error or different errors in productions). Qualitative analyses examined error types and explored the effect of target words' characteristics on inconsistency. Children with IPD produced 52% of words with different errors. While 56% of all phoneme errors were developmental (age appropriate or delayed), atypical errors typified inconsistency: default sounds and word structure errors. Words with more phonemes, syllables and consonant clusters were vulnerable to inconsistency, but their frequency of occurrence had no effect. TD children and those with IPD had different quantitative and qualitative error profiles, confirming IPD as a diagnostic category of SSD. Qualitative analyses supported the hypothesised deficit in phonological planning of words' production for children with IPD.

Two-year-old phonology: impact of input, motor and cognitive abilities on development.

Previous research has rarely compared the contributions of different underlying abilities to phonological acquisition. In this study, the auditory-visual speech perception, oro-motor and rule abstraction skills of 62 typically developing two-year olds were assessed and contrasted with the accuracy of their spoken phonology. Measures included auditory-visual speech perception, production of isolated and sequenced oro-motor movements, and verbal and non-verbal rule abstraction. Abilities in all three domains contributed to phonological acquisition. However, the use of atypical phonological rules was associated with lower levels of phonological accuracy and a linear regression indicated that this measure of rule abstraction had greater explanatory power than the measures of input processing and output skill.

Phonological awareness and language intervention in preschoolers from low socio-economic backgrounds: a longitudinal investigation.

This study examines the literacy outcomes for children from socially disadvantaged backgrounds who had received specific whole-class phonological awareness (PA) and language intervention in preschool. The participants were 57 children who had been involved in the original intervention study. Their PA skills, letter-sound knowledge, real word and non-word spelling and reading comprehension were assessed in Grade 2. The results indicated that children who had received intervention in preschool performed similarly to the children who had not received intervention. The gains made in PA and language skills post intervention had failed to augment further literacy development. A post hoc examination of individual student profiles, however, revealed that a subgroup of children who had received intervention had maintained their enhanced performance and that the intervention cohort had similar scores on tests of PA ability to their age-matched peers in the population. It was concluded that whole-class, teacher-delivered, PA and language intervention, while effective in the short term, does not lead to a generalized improvement in literacy skills in Grade 2. Possible reasons for the failure of the program to produce medium term gains are discussed.

Perception of the auditory-visual illusion in speech perception by children with phonological disorders.

An example of the auditory-visual illusion in speech perception, first described by McGurk and MacDonald, is the perception of [ta] when listeners hear [pa] in synchrony with the lip movements for [ka]. One account of the illusion is that lip-read and heard speech are combined in an articulatory code since people who mispronounce words respond differently from controls on lip-reading tasks. A same-different judgment task assessing perception of the illusion showed no difference in performance between controls and children with speech difficulties. Another experiment compared children with delayed and disordered speech on perception of the illusion. While neither group perceived many illusions, a significant interaction indicated that children with disordered phonology were strongly biased to the auditory component while the delayed group's response was more evenly split between the auditory and visual components of the illusion. These findings suggest that phonological processing, rather than articulation, supports lip-reading ability.

Two-year-olds' phonological acquisition: Normative data.

The study reported evaluated an assessment of phonology for 2-year-olds to establish normative data and determine if early identification of children with speech difficulties is possible. The study evaluated 62 2-year-old children on the Toddler Phonology Test (TPT). Children produced 32 words, spontaneously or in imitation. Ten of the children were assessed three times, on the third occasion, when they had reached 3 years, on another phonological assessment. The data indicated that older children performed better than younger children on quantitative measures. Girls and boys performed equally well. Their phonetic repertoires were missing some fricatives and all affricates, as well as /r/. Consistently used error patterns identified included cluster reduction, final consonant deletion, stopping, fronting, weak syllable, deletion, gliding and deaffrication. Correlation analyses indicated that performance at the first assessment on the TPT indicated performance on subsequent assessments. While quantitative data was not a reliable predictive indicator of speech disorder, qualitative analysis of error types was predictive, with children who made many atypical errors at 2 years being diagnosed as phonologically disordered at 3 years. The findings provide initial evidence that direct formal assessment of 2-year-old phonology is possible.

The impact of selecting different contrasts in phonological therapy.

Previous research indicates that the extent of progress made by children with phonological disorders depends upon the nature of the word pairs contrasted in therapy. For example, phonemes that differ maximally in terms of place, manner, voicing and sound class (e.g., fan - man) in comparison to therapy where the word pairs presented differ minimally (e.g., fan - van). To investigate the implications of target selection within a typical clinical context (as opposed to a rigorous research setting) eight speech-language pathologists implemented intervention with appropriate children from their caseloads. Nineteen children each received 6 hours of therapy over one school term. They were randomly allocated to two groups. One group (of nine children) received intervention based on a traditional minimal pair approach, targeting homonymy as well as distinctive feature contrast. The other group (ten children) received intervention targeting contrasts differing across a range of distinctive features. Children made considerable progress in therapy in terms of speech accuracy and number of error patterns suppressed. However, there was no difference between the progress of the two groups. Follow-up assessment of 14 of the 19 children indicated maintenance of progress by both groups. Reasons for the lack of difference between the groups in the current study are considered and clinical implications are drawn.

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 [Formula: see text] when they hear [Formula: see text] presented in synchrony with the lip movements for [Formula: see text]. 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.