Naming
Children are often asked to name pictures in order to collect information about their speech production. Two commonly used assessments o f speech production that use naming are the Edinburgh Articulation Test (Anthony, Bogle, Ingram & Mclsaac, 1971) and the South Tyneside Assessment o f Phonology (Amstrong & Ainley, 1988). The child must rely on his/her own phonological representation and motor program in order to name pictures. (The motor program is here considered to be the stored set of
instructions for the articulatory gestures required to achieve an acceptable pronunciation o f the word (Stackhouse & Wells, 1997)). Once the motor program has been accessed, output processing levels o f motor planning and motor execution then result in the word being spoken (see Figure 3.4). STM requirements o f naming are minimal, as the child has the picture readily available, has access to a stored lexical representation o f the word, and is only responding to one item at a time.
Word Repetition
Repeating words may tap different processes to a naming task. There are two ways in which a child may process words for repetition The child may use existing lexical representations to discriminate and recognise the word heard and then access the motor program for the spoken response. Other levels o f output processing, i.e. motor planning and execution, are also involved (see Figure 3.5). However, the child may not use existing lexical representations, but rather use bottom-up input processing skills to perceive the spoken word presented for repetition and then utilise motor programming skills for the creation o f a motor program for output (in a similar way to repeating a non-word, as discussed below).
A child may repeat some words more accurately than he names them, if his motor programs are inaccurate or incomplete. He may name pictures more accurately than he repeats the same words, as auditory discrimination skills are implicated in the repetition. So, if the child misperceives the word to be repeated then an incorrect response may be given. As with naming, STM requirements are minimal with only one stimulus to retain and repeat, and, if the child recognises the word, top-down processing will allow long-term storage to refresh STM, if required.
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zr "Ro i-s wNon-word Repetition
In order to examine the child's speech production skills without interference from existing lexical representations, non-words can be presented for repetition. Within the framework o f psycholinguistic assessment comparison o f the repetition o f words with repetition o f non words can aid the analysis o f a child’s speech processing profile. In order to compare performance more thoroughly, it may be useful to match the non-words closely with the words, so that phonological complexity and articulatory difficulty on the two sets o f stimuli is equitable. A non-word may contain the same consonants as a word, e.g. /b rij/ is matched to
‘brush’, or the consonants o f a non-word may be matched with those o f a word in terms o f phonetic properties, e.g. /glougoz/ is matched to ‘crocus’
(Ryder 1991). Within a psycholinguistic approach these two classes o f stimuli are considered to have different processing requirements. When words are presented a child can use his lexical representations (semantic, phonological and orthographic) to help him to complete the task. When non-words are presented the child does not have an existing lexical representation, and, in particular, an existing motor program, to use to produce the non-word. However, there is evidence that children’s performance will be affected by how similar a non-word is to a known word. (This issue o f word-likeness effects on NW R will be further discussed in Chapter 4.)
To repeat a non-word, the child must be able to discriminate and perceive the sounds within the heard stimuli. This phonological information is, presumably, then retained in a temporary store (possibly the phonological loop component o f WM). A new motor program must be created in order to articulate a word that has not been said before. Other levels o f output
processing, motor planning and execution, are also involved (see Figure 3.6). However, within the psycholinguistic framework, this task is viewed as taxing motor programming skills in particular. There is some debate about the STM requirements o f NWR. Some researchers (e.g. Gathercole and colleagues) would argue that NWR reflects STM skills. Indeed the use o f the NW R task in STM research has already been discussed in Chapter 1. There will be further discussion o f this task as a measure o f STM and o f speech processing in the following chapter. Chapter 4.
Children may repeat words more accurately than non-words if they use accurate, existing motor programs for output in word repetition. This difference in performance may be particularly marked if the child has a motor programming deficit. They may repeat non-words more accurately than words if existing motor programs are inaccurate, and satisfactory motor programming skills allow the creation o f accurate, new motor programs for the non-words.
Differences in Performance across Tasks
There is evidence from studies involving children with speech and / or language difficulties o f differential performance across these three speech production task paradigms: word repetition, non-word repetition and naming.
When investigating children with different symptoms o f speech disorder, Wiliams and Chiat (1993) found different profiles o f task performance. A group with phonological delay had similar error scores across the three measures o f speech production. A group with phonological disorder showed significant differences in percentages o f errors between tasks, with
the lowest percentage o f errors made on the word repetition task and the highest percentage errors in the naming task.
Dodd, Leahy and Hambly (1989) also reported similar patterns o f performance on naming and word repetition in children with phonological delay. Two groups o f children with phonological disorders, who showed either inconsistent or consistent error patterns in their speech, were significantly more accurate in repeating words, than in naming pictures. These authors had considered that repetition would be the easier task as children did not need to access lexical representations, whilst picture naming required the accessing o f lexical representations and the generation a plan for production (akin to the notion o f the motor program). Bradford and Dodd (1994) found that the phonologically disordered children who made inconsistent errors were significantly poorer at a NW R task than children whose speech errors were consistent.
Thoonen, Maassen, Gabreels, Schreuder and De Swart (1997) found that two groups o f 6-7 year-old children with dyspraxia and with normal speech made significantly more errors in non-word than word repetition. The dyspraxic children were also significantly poorer at both tasks than the control group. Gathercole and Adams (1993) found that performance on word and non-word repetition was significantly correlated in 2 to 3 year- old children with normally developing speech.
In addition to these group studies, the same range o f tasks have also been used in single case studies to examine speech processing skills o f children with speech difficulties. The individual subjects o f some o f these case studies have shown different profiles o f performance. A case reported by
Bryan and Howard (1992) showed more accurate NWR than word repetition or naming. Stackhouse and Wells (1993) investigated a child who showed more accurate word repetition than naming. Whereas, Chiat and H unt’s (1993) case showed a very similar performance across the 3 speech production tasks. The authors o f these studies use these different profiles o f speech production performance to infer a particular speech processing deficit that underlies the child’s speech disorder.