Nonword Repetition and Sentence Repetition as Clinical

Markers of SLI: The Case of Cantonese

Stokes, F. S., Wong, M.Y.A., Fletcher, P., & Leonard, B. L. (2006). Journal of Speech, Language, and Hearing Research, 49, 219-235.

Research has shown that English speaking children with SLI score

lower than their age-matched typically developing peers (TDAM)

and language matched typically developing peers (TDLM), on tests of

working memory.

For this reason research has focused on both :

1. Phonological working memory via tasks of nonword repetition

(NWR) and sentence repetition (SR)

2. Functional working memory

Purpose: Recent research suggests that NWR & SR tasks can be used as clinical markers to discriminate between children with SLI and their TDAM &TDY peers.

Although children with SLI scored significantly lower than their TDAM and TDY peers on NWR tasks it is not known what underpins the difference .

It is claimed that working memory deficits underlie the poor performance of children with SLI, but research has shown that there are more factors to consider:

1 .The lexicality effects of NWR stimuli

2 .The phonological structure of the language under investigation

3 .prosodic influences

The researchers in this article sought to explore the issues of prosodic structure and lexicality effects by investigation of NWR in Cantonese, where prosodic structure is not an issue.

SR tasks have long been part of a screening battery for the identification of language impairment .

The authors suggested that the source of the difficulties on SR could be

either general working memory deficits or “deficit in linguistic

processing”.

Conti-Ramsden at al., (2001) said that SR must tap a child’s knowledge, whereas NWR does not.

If Cantonese speaking children with SLI have no difficulty with tests of NWR & SR then it is possible that the differences found in previous studies between TDAM & SLI groups may be due to differences in language ability rather than in working memory.

Means and between-group differences on the language measures

TDAMTDYSLIF (2,41)

N (=44)(15)(15)(14)

1 .CRDLS-R56.5341.7342.6470.26b

.17a

2 .CRVT60.1347.0750.5039.86b

3.1a

3 .MLU4.493.973.708.37b

.99a

1 .CRDLS-R: The Cantonese version of the Reynell Developmental Language Scales.2 .CVRT: The Hong Kong Cantonese receptive vocabulary test.

3 .MLU: The mean length of utterance .

24 nonwords were constructed for this study

6 for each of the 4 syllable lengths

The syllables selected for the nonwords do not occur in the Cantonese language .

Four syllable lengths: CVC, CVCVC, CVCVCVC, & CVCVCVCVC

The selection process that the researchers used resulted in:

IN syllables (CV combinations that occur in Cantonese syllabary)&

OUT syllables (CV combinations that did not occur in Cantonese).

Task: NWR of IN nonwords and OUT nonwords were compared.

SR performance was compared using 2 sentence types and 4 different scoring methods;

The 2 sentence types were either 9 or 10 syllables in length :

1 .Aspect-marker - sentences contained the elements of subject, verb, aspect marker, and object; e.g:

go3 naam4 zai2 hou2 daai6lik6 caat3 gan2 deoi3 haai4

(The boy is polishing the shoes very hard. )

2 .The Passive - contained the passive elements. e.g:

Ceong4 tau4faat3 go3 naam4zai2bei2 zek3 gau2 zeoi1

(The boy with long hair was chased by the dog.)

Four methods of scoring for the SR task: ) 8 sentences for each sentence type)

1 .Complete sentence correct: The participant scored a point for each sentence repeated correctly, with the inclusion of all sentence elements .

2 .Core elements correct: A point was given if the child's repetition of the sentence included all of the core elements of both sentence types .

Core Elements: Aspect: verb + aspect marker + noun

Passive: be + agent + verb

3 .Error method: was used to equate the researcher's results with those for English (Conti-Ramsden et al., 2001). The less errors the child made, the more points he received. (0-3 points).

4 .Percentage syllables correct method: The calculation of the percentage of correct syllables, i.e. one point was given for each correct syllable .

Both the NWR and SR tasks were randomized.

The NWR task:

The Goal: to repeat the word exactly as it was heard .

Trial items: 2 words and 2 nonwords .

The test items were presented in order of increasing difficulty: one syllable nonwords

followed by two syllables nonwords, etc .

The SR task :

The Goal: to repeat the sentence exactly as it was heard .

There were three trial items.

In the case of both tasks the trial items were repeated once in case of an incorrect

response but no experimental items were repeated .

Both tasks were administrated via free-field speakers and all responses were recorded.

Group1 syllable2 syllables3 syllables4 syllablesTotal % Correct

TDAM74.5176.2268.7361.7368.35

TDY69.8065.7756.9844.8155.76

SLI77.3175.9561.5652.3862.99

Total73.7972.5762.4452.9862.35

1 .Significant differences were found among the groups on total % correct.

2 .The test of NWR was age sensitive, but did not distinguish between the children with SLI and their age-matched peers.

Means in percentage for all syllable lengths on the non-word test for the participant groups.

One syllable IN88.8966.6783.33

One syllable OUT51.1148.8857.14

Two syllable IN78.8958.8971.43

Two syllable OUT55.5637.7859.52

Three syllable IN62.8651.4354.08

Three syllable OUT48.4734.5541.56

Four syllable IN63.3346.0057.14

Four syllable OUT26.1916.1921.42

CV structure TDAM TDY SLI

Results:1 .The TDAM and the SLI group scored significantly higher than the TDY group on total

NWR, on repetition of IN non-words and repetition of OUT non-words .

2 .There were no significant differences between the TDAM and the SLI groups .

Scoring Method:

Sentence Type:TDAM:TDY:SLI:

Complete sentence correct

Passives Aspect

45.83 43.33

23.67 16.67

19.64 15.17

Core elements correct

Passives Aspect

89.17 83.33

70.33 61.67

71.43 46.43

Error scoringPassives Aspect

73.61 73.33

44.72 44.44

44.94 38.69

%of syllables correct

Passives Aspect

93.24 95.17

74.70 76.33

76.81 77.86

Means for percentage of accuracy of SR for the three participant groups.

ERROR METHOD:

Test ResultsSLITDAM

Positive110

Negative 315

Classification of children with SLI and their TDAM peers as typically developing or language impaired on a SR task.

%OF SYLLABLES CORRECT METHOD:

Test ResultsSLITDAM

Positive60

Negative 815

We can conclude that SR composed of passive and aspect sentences and scored by the error method may be a viable clinical marker of Cantonese SLI.

NWR Task:

Both the SLI and TDAM groups scored higher than the TDY group .

no difference between the SLI group and the TDAM group

The two groups also scored the same on OUT nonwords .

SR Task:

On the SR task, the TDAM group scored higher than the SLI and TDY groups, who did not differ .

Methods of scoring SR: the best measure was the Error Method which

successfully distinguished between TDAM and SLI groups and should be

further evaluated as a clinical marker of SLI in Cantonese!

No correlation was found between performance on NWR and performance on SR

In this study.

If children with SLI were shown, across languages to have deficits in NWR and/or

SR, then we would be one step closer to uncovering the cognitive mechanisms that

contribute to language impairments.

Research with English-speaking children has shown a significant difference between children with SLI and their TDAM &TDY peers on tests of NWR .

This poorer performance has been attributed to a: language-independent working memory constraint.

We expect, then, that a working memory constraint, might be identified in other groups of children with SLI, regardless of the language.

However, although NWR is a sensitive developmental test in Cantonese with older children scoring higher than younger children, there is no difference in performance between children with SLI and their TDAM peers.

This may suggest that a working memory capacity limitation of the type believed to underlie NWR skills does not underpin language impairment in Cantonese speaking children.

Given the range of scoring methods used for SR tasks across studies, it was important to compare the effects of using one method over another .

Awarding points according to the number of errors per sentence proved to be the most effective method, as it successfully differentiated between children with SLI and their TDAM peers.

It is also important to consider the types of sentences chosen for the test:

Application of two sentence types (aspect and passive) together proved to be the best identifier of SLI in this cohort while ensuring sufficient sentence complexity to avoid ceiling performance in the TDAM group.

SR has the potential to be a useful clinical marker of SLI in Cantonese, as it is in English.

Further work might explore prosodic and processing factors in cross-linguistic studies.

According to Vance and Plante (1994), it was suggested that measures that have discriminated accuracy above 90% were considered: good discriminators

and those measures that have above 80% were considered: fair discriminators.

The recommended accuracy should be above 80% .

Sensitivity for the best method used in SR task was only 77%, and thus below the 80% recommended. Field testing with a larger sample is necessary!