Abstract:
Phonotactics, which accounts for sound patterning, is affected by language regression in
children with autism. Existing linguistic studies on autism in Nigeria focused mainly on
general description of the disorder and developmental challenges. However, little
attention was devoted to systematic description of their phonological patterns.
Therefore, this study was designed to examine the speech production of autistic children
in Lagos State, Nigeria, with a view to describing the phonological processes involved
in the production of phonemes and syllables and the constraint ranking responsible for
them.
Alan Prince and Paul Smolensky’s Optimality Theory served as the framework, while
the descriptive design was adopted. The convenience sampling technique was employed
to select four special-needs facilities in three local government areas (Amuwo-odofin,
Badagry, and Ikeja) of Lagos State. Availability of and accessibility to relevant data
necessitated the selection of the facilities. Twenty-four children with autism under the
age of 17 years (Amuwo-odofin: 17, Badagry: 2, and Ikeja: 5) accessing the facilities
were purposively selected. Speeches of the participants were audio-recorded twice a
week for two years. The data were subjected to phonological and acoustic analyses.
Three phonological processes were dominant: deletion, substitution and epenthesis.
Vowels were generally modified. Deletion was dominant in the rendition of consonants,
with the lateral sound /l/ mostly affected. Substitution and epenthesis affected mainly
vowels. Central vowels /ᴧ, ɜ, ə/ were strengthened and /ɔ/, /e/, /æ/ were used for each,
respectively. Epenthesis was prominent in the realisation of vocalic phonemes, with /ɪ/
and /ə/ substituted as /i:/ and /æ/, respectively. It was also dominant in the articulation
of triphthongs /eɪə/ and /ɔɪə/. Monophthongs were either retained or substituted with
long or strong vowels. Diphthongs were monophthongised or substituted with stronger
versions. Triphthongs were either substituted with diphthongs or epenthesised with an
intrusive /j/, creating disyllabic sounds. With regard to syllables, simple onsets were
produced comfortably more than complex onsets, while both simple and complex codas
were deleted, reduced or produced with great difficulty. Constraint ranking favoured
markedness over faithfulness. The constraints responsible for vowels were *SCHWA,
NOCODA, NODIPH and *HIATUS. *COMPLEX ONSET and *COMPLEX CODA
were the markedness constraints accountable for the simplified outcome of complex
onsets, complex codas, open and closed syllables. *HIATUS was ranked above MAXV for the emergence of minimum syllables. Consonant clusters, especially at coda
positions, were reduced or rendered open, as *COMPLEX CODA was preferred above
MAX. There were inconsistencies in the intensity values. The values were either
abnormally high (73.94dB) or low (52. 89dB). Against a threshold of 63.42dB, their
pitch values were either extremely high or low.
The phonotactics of autistic children in Lagos State, Nigeria is characterised by
simplification of difficult phonemes and syllables through deployment of deletion,
substitution and epenthesis. Therefore, multidisciplinary therapists should be employed
to improve the treatment and rehabilitation of autistic children.