This summary is produced by the Cued Speech Association UK from a translation of the French presentation text. Whilst every effort has been made to ensure that it gives an accurate flavour of the presentation, a copy of the official Congress Report is now available (in French) for those who would like the full and precise wording.
Our grateful thanks go to Dr. Murielle D’Hondt for her permission to reproduce this text and to Pat Coves for her translation of information. LPC is the name for the French-language version of Cued Speech and the terms ‘Cued Speech’ and ‘LPC’ are interchangeable in the context of this summary.
Murielle D’HONDT is a Doctor of Psychological Sciences and currently works as Speech and Language Therapist, whilst also undertaking research at the Laboratory of Experimental Psychology at Université Libre in Brussels.
In the Autumn of 2000 the Cued Speech Association UK Newsletter reported on her preliminary research into the fascinating and important topic of hemispheric specialisation and early linguistic experience amongst deaf people.
It is important for the optimum language development of deaf children that their development in this area echoes that of hearing children. The update of her research, presented at the Congress, underlines the importance of early, accessible language for deaf children.
In her introduction Murielle D’HONDT reminded us: ‘As you know, our brain is composed of two hemispheres. These are associated traditionally with different functions. So, the left hemisphere is specially involved in linguistic processes (speaking, understanding,…) whilst the right hemisphere is particularly involved in visualspatial processing (drawing, map-reading,…)’.
Thus, in right-handed hearing people the left hemisphere processes language (the opposite being the case for some left-handed people). In the past, researchers looked at whether deaf people, who use a visual language, process that language using the left (language) hemisphere or the right spatial) hemisphere. They found that deaf children of deaf (signing) parents also use the left hemisphere when they sign.
However, the language development of deaf people is not always concentrated within the left hemisphere. Murielle D’HONDT’s research looks at the influence of early language on hemispheric specialisation with both signers and users of LPC.
‘In our research, we tested groups of deaf people who had benefited from early exposure to language against groups of deaf people not having had the benefit of such an early exposure.’
LPC is the name of the French-language version of Cued Speech. The first test looked at receptive language in four different groups of people, all of whom were right-handed and profoundly deaf from birth.
1) Deaf people with deaf parents. They are native signers (LS+).
2) Deaf people with hearing parents. They acquired Sign Language after they started school (LS-).
3) Deaf people whose parents, being hearing, made early (before the age of 3) and intensive (more than 50% of conversations) use of LPC with their child (LPC+).
4) Deaf people with hearing parents. However, LPC was used later (after the age of 3), in a less intensive way and often in the less advantageous context oof school (LPC-).
The experiment, based on video images, used the fact that the nervous channels, working as visual hemifields, are crossed and it tested responses to both words (linguistic condition) and to spatial stimulus (non-linguistic). As predicted, it found that:
1) The LPC+ group give more correct responses for the linguistic condition when the words are presented in the right visual hemifield. This indicates specialisation of the left hemisphere for performing this task. However, their performances are comparable in the two hemifields for the non-linguistic condition.
2) The LPC- group do not demonstrate hemispheric specialisation, either for the linguistic condition or for the non-linguistic condition.
3) The LS+ group have better performances in the midst of the right visual hemifield for the linguistic condition, indicating left hemispheric specialisation; but reply equally well in the left as in the right (showing no such specialisation) for the non-linguistic condition.
4) The LS- group demonstrate no significant difference between their response to the linguistic or the non-linguistic condition.
It can therefore be concluded that where deaf children have early exposure to language (either sign or using LPC) they are able to develop a superiority of the left hemisphere. This mirrors that of hearing people exposed to spoken language. However, this does not happen with late exposure to either LPC or sign.
A different experiment looked at language production. The test used the principle that two brain activities undertaken at the same time interfere with one another. The groups tested were the four categories of the previous test with the addition of hearing people. All had to repeat, while undertaking another task,
1) words (spoken, signed one-handed, or cued) – the linguistic test
2) grimaces – the non-linguistic test.
The other task involved tapping as quickly as possible at a telegraphic key. The interference –or not – of the first task with the second demonstrated which hemisphere was processing the words or grimaces. The results showed that the deaf LPC+ group had comparable results, on all points, with those of the hearing group. However, the deaf LPC- group, whilst comparable with the hearing group results when imitating grimaces, had results which demonstrated no hemispheric specialisation for linguistic tasks.
The same contrast is shown between the LS+ and the LS- groups. The first group show results comparable to that of hearing people, the second do not.
In conclusion, both tests demonstrate that early and intensive exposure to full language establishes left hemisphere specialisation for language in the minds of deaf people, echoing that of hearing people, but that later exposure does not have the same result.
