Conclusions.

2.9.1. Minimal-pair discrimination.

The following points, developing the pilot test for the main phase, are proposed:

1. The discrimination of naturally-produced minimal-pair stimuli allows an ecologically-valid evaluation of the speech-perceptual abilities of subjects differentiated by reading-status or by chronological age. The minimal-pair pilot indicated that SRD-children have occasional difficulties with the discrimination of certain phonemes in item-initial position under quiet listening conditions. The addition of low levels of background noise is apparently unnecessary for the generation of discrimination errors in SRD-children for certain types of phonemic contrast. Minimal-pair discrimination of naturally-produced real-word items will be included in the main test battery.

2. The procedure of having subjects repeat the word-pair before making their discrimination judgement was to be discontinued for the main phase experiments. Item-repetition may have entailed production as well as perceptual errors, and was considered capable of distracting attention from the discrimination task in subjects for whom the overall response-requirements might represent a heavy loading within "working STM".

3. Full-scale experiments in the main test battery will comprise "same" - "different" discrimination judgements expanded to cover a much wider range of phoneme-contrasts differing by only one feature, and recorded with a quiet background. The use of intervocalic (VCV) minimal-pairs will enable the study of a wider range of contrasts than would be possible if real-word stimuli were to be used, since the selection is free from vocabulary control. If, using VCV items, those consonants which prove to be accurately discriminated by the reading- impaired group are those which are relatively early-acquired, and these children are less accurate at discriminating those items which are mostly later-acquired, an

explanation based on "developmental delay" would be plausible.

4. Of further interest will be to examine whether, for SRD-children, there are circumstances in which perceptual confusion can be shown for contrasts differing by more than a single feature.

5. Since some consonant contrasts differing in only one feature were well discriminated by all reading-groups in the first pilot test (such as the /dai/-/gai/ plosive place contrast) contrasts will be presented in different vowel-contexts to examine the effect of this on discrimination accuracy. This will be referred to as the “natural minimal-pairs” test.

2.9.2. Real-word and nonword repetition.

As stated above, there is no estimate from the Alpha 7 (source) listings on the relative frequency of the words chosen for this test in the written vocabulary of language-normal children. Therefore it is not possible to control for differential effects of familiarity or frequency on the accuracy of their repetition. The fact that words such as "vase" and "lend", which would be of relatively low frequency even in the spoken vocabulary of adults, appear in the listings suggests that the errors associated with their repetition could be frequency-related, particularly for SRD children. They made several errors in the repetition of these two words, but the control groups did not. It was therefore decided not to ask subjects repeat real words in the main test-battery.

The nonword repetition test was, however, retained for items of greater syllabic length. The production of multi-syllabic nonsense words by different reading- groups will be studied in a replication of Gathercole et al's (1994) “CNRep” test. This will examine whether, as reported by the authors, dyslexic children make more errors in repeating the longer items (those of three syllables and more) than do CA- and RA-control children. Snowling and Hulme (1994) have emphasised that nonword repetition skills are related to learning the spelling and fluent

pronunciation of new words. Persistent problems with nonword repetition were regarded as tied to persistent difficulties with speech processing (phonological skills) in general. Developmental phonological dyslexies, such as Snowling and Hulme's subject JM, quite systematically mispronounce consonants. Although there is evidence that not all nonwords of a given length are equally difficult to decode (Treiman, Goswami and Bruck, 1990), it may be the case that children who are particularly weak at nonword reading may also be weaker than other SRD-children at nonword repetition. Therefore, the other main aim in using this test is to investigate this possibility. In other words, would the error pattern for the repetition of longer non words assist in the sub-grouping of the sample of reading-disabled children ? That this may not prove to be demonstrable could be related, say, to the incidence of vowel digraphs in a sample of nonwords, which may present more

consistent difficulties for groups of SRD children as a whole than the pronunciation of consonants,

2.9.3. Initial-phoneme deletion.

There was a very strong effect of group for the phoneme-deletion task, although individual experimental children differed widely in the extent to which they could execute this task. As it is so central to the difficulties of SRD-children with tasks involving some form of segmentation and/or blending of phonemes, phoneme deletion for such children becomes an operationally complex and potentially stressful task. This appears to be so whether or not a time limit for responding is imposed.

The conclusion could reasonably be drawn that problems arise because phoneme deletion is more closely related to these subjects' widespread difficulties with the representation of phonology (hence to decoding problems themselves) than to specific individual differences in speech perceptual acuity. In fact, the pilot test result did suggest that this procedure had little potential for distinguishing those SRD-children who, from the minimal-pair pilot data, had certain speech- discriruination problems from those who did not. The high refusal rate observed

fo r several children suggested the experience o f stress, as was also clear from post­ test comments. Phoneme deletion showed the largest degree of individual difference and the highest mean error rate of the three chosen pilot tests for the SRD children. It may have been possible to proceed with this measure in the main phase by considering a modification of the initial phoneme deletion task requiring no verbal response. The Lindamood Colour Blocks test (Lindamood and Lindamood, 1979) would have involved the removal of the first of a line (the leftmost) of differently coloured blocks said to represent the phonemic structure of items. This option was rejected because, although a verbal response would not be required, the need to mentally separate the first segment from each item heard would remain. However, the same perceptual decision is required, and it is this which creates the difficulty for SRD children, not the response mode. Based on the need to ensure the willingness of children to continue to participate in the entire test-battery, it was concluded that no further use should be made of this procedure.

CHAPTER 3.