Research into Phonological Mean Length of Utterance (pMLU)

Research into Phonological Mean Length of Utterance (pMLU) Specific language impairment (SLI) is a disorder defined by exclusion. Children with SLI exhibit language difficulties in the absence of other factors, such as hearing loss, mental impairment, physical impairment, emotional disturbance, or environmental deprivation (Bishop, 1992a, 1992b; Lubert, 1981). Children with SLI have difficulty acquiring one or more of the components of language, i.e. form (phonology, morphology, and syntax), content (semantics), and use (pragmatics). The field of phonological acquisition has made extensive efforts to measure its development through normative studies (Templin, 1957; Olmstead, 1971) and articulation tests (Hodsen Paden, 1991). Earlier, the research focus was on correctness of consonants as well as the analysis of segments in general. Recently the whole word complexity has been stressed (Masterson Kamhi, 1992, Ingram, 2002). One such measure is the Phonological mean length of utterance (pMLU). It is a whole word measure for measuring phonologic al proficiency (Ingram,2002). It measures the length of a childs words and the number of correct consonants. The pMLU for a speech sample is calculated by: (1) counting the number of segments (consonants and vowels) in each word as produced by the child; (2) counting the number of consonants produced in each word that the child produced accurately; (3) summing these two numbers; (4) totaling these sums; and (5) dividing this total by the total number of words in the sample. pMLU quantifies development of phonology and focuses on the childrens whole-word productions instead of specific segments. Ingram demonstrates the value of the pMLU measure by applying it wide range of contexts. NEED FOR THE STUDY Although pMLU has been addressed in normal as well as phonological disorders and cochlear implanted children, the same is not focussed on children with SLI. Since PMLU is a whole word measure, problems in phonology and morphosyntax are expected to reduce the score. Hence PMLU can be used to investigate the difficulties if any in phonology and morphosyntax of children with SLI. Hence the present study was planned. AIM OF THE STUDY: To compare the pMLU of children with SLI in comparison with typically developing Kannada speaking children. METHOD: This study followed a case control design. Participants were divided into 2 groups. Clinical group comprised of six individuals (5 males 1 female) with SLI in the age range of 4 to 6 years. The diagnosis of SLI was done on the basis of Leonards exclusionary criteria and the informal assessment of morpho-syntax by the primary investigator. The control group comprised of age matched 30 children out of which 15 were males and 15 females. Exclusion criteria considered were speech, language, hearing and neurological problems. A minimum of 50 spontaneous speech utterances were elicited from each child for a duration of 30 to 40 minutes which was audio recorded using SONY recorder. The childrens utterances were narrow transcribed and pMLU was calculated for each word produced by the child. The sum of each word in all the utterances were totalled and divided by the number of words produced by the child to obtain the pMLU scores. pMLU was calculated for all the children in both the groups. Mann Whitney U test was administered to find out the significant differences between the means of both the groups. RESULTS: The results of the Mann Whitney U Test revealed a statistically significant difference between the means of pMLU scores across the group at p DISCUSSION: pMLU is a whole-word measure for phonological development. The results of the present study revealed that the pMLU scores for the children with SLI were lower in comparison to children with normal language development. This could be attributed to the increased number of incorrect consonants in the speech of clinical group when compared to the control group. The decrease in pMLU scores in the clinical group could also be due to the deficit in the use of morphosyntax as these children were having morphosyntactic errors. This in turn suggests that children with SLI are inferior in the acquisition of segments and in their whole-word phonological proficiency to typically developing children. As this pMLU measure includes the number of segments in a word, pMLU can be used to indicate morphosyntactic abnormalities in children with SLI. This tool can also serve as an aid for monitoring the progress of a child when assessed pre and post therapeutically. CONCLUSION: The present study investigated pMLU in children with SLI in the age range of 4-6 years. The results revealed that children with SLI are inferior in the acquisition of segments including morphemes as well as in their whole-word phonological proficiency than the typically developing children. Hence, pMLU measure could be regarded as a yardstick for phonological and morphosyntactic development in children with SLI. INTRODUCTION: SLI is a disorder defined by exclusion. Children with SLI exhibit language difficulties in the absence of other factors, such as hearing loss, mental impairment, physical impairment, emotional disturbance, or environmental deprivation (Bishop, 1992a, 1992b; Lubert, 1981). Specific language impairment (SLI) has been estimated to affect approximately 7 percent of children (Leonard, 1998; Tomblin et al., 1997) and to persist into adolescence (Aram et al., 1984; Beitchman et al., 1996; Stothard et al., 1998;Johnson et al., 1999). Children with SLI have difficulty acquiring one or more of the components of language, i.e. form (phonology, morphology, and syntax), content (semantics), and use (pragmatics). However, as a group they show disproportionate difficulty with some areas, performing worse than typically developing children matched on vocabulary level or mean length of utterance. Several authors (eg, Leonard et al.,1992; Rice et al., 1995; Rice and Wexler, 1996; Oetting and Horohov, 1997; van der Lely and Ullman, 2001) observe that this is particularly the case in the area of verb morphology and it has also been reported in some areas of syntax, including the comprehension of passive sentences (Bishop, 1979; van der Lely and Harris, 1990; van der Lely, 1996) and formation of wh-questions (Leonard 1995; van der Lely and Battell, 2003). The field of phonological acquisition has made extensive efforts to measure its development through normative studies (Templin, 1957; Olmstead, 1971) and articulation tests (Hodsen Paden, 1991). Earlier studies have focused on correctness of consonants as well as the analysis of segments in general. Recent studies have focused on the whole word complexity (Masterson Kamhi, 1992, Ingram, 2002). One such measure is the Phonological mean length of utterance (PMLU). It is a whole word measure for measuring phonological proficiency (Ingram, 2002). It measures the length of a childs words and the number of correct consonants. The PMLU for a speech sample is calculated by: (1) counting the number of segments (consonants and vowels) in each word as produced by the child; (2) counting the number of consonants produced in each word that the child produced accurately; (3) summing these two numbers; (4) totaling these sums; and (5) dividing this total by the total number of words in the sample. PMLU quantifies development of phonology and focuses on the childrens whole-word productions instead of specific segments. Ingram demonstrates the value of the PMLU measure by applying it in a wide range of contexts. These include a comparison of monolingual children, a comparison across languages, and the diagnosis of impairment or delay. Very few studies have addressed the PMLU in different languages. One such study is by Ingram (2002) who proposed preliminary PMLU stages, reflecting the possible level of development in English speaking children which are as follows. Helin, Makkonen Kunnari (2006) reported that PMLU was much higher in Finnish speaking children than those reported for children acquiring English. Balasubramanium bhat (2009) reported the same in kannada speaking typically developing children. Other studies have focused PMLU on the disordered population. Schauwers, Taelman, Gillis Govierts (2005) reported lower PMLU scores in children with cochlear implant than age matched typically developing peers and they also concluded that the earlier implanted children were more proficient than the later implanted children. Prasad, Hossabetu, Balasubramanium Bhat (2010) studied phonological mean length of utterance in children with phonological disorder and they reported, children with phonological disorder are inferior in the acquisition of segments as well as in their whole-word phonological proficiency than the typically developing children. NEED FOR THE STUDY: Although pMLU has been addressed in normal as well as phonological disorders and cochlear implanted children, the same is not focussed on children with SLI. Since PMLU is a whole word measure, problems in phonology and morphosyntax are expected to reduce the score. Hence PMLU was used to investigate the difficulties if any in phonology and morphosyntax of children with SLI. Hence the present study was attempted in this direction. AIM OF THE STUDY: To compare the pMLU of children with SLI in comparison with typically developing Kannada speaking children. METHOD Participants The study followed a case control design. Participants were divided into 2 groups i-e the control group and clinical group. Clinical group comprised of six individuals (5 males 1female) with specific language impairment in the age range of 3 to 6 years. The control group comprised of age matched 30 children out of which 15 were males and 15 females. The diagnosis of specific language impairment was done on the basis of Leonards exclusionary criteria and the informal assessment of morpho-syntax by the primary investigator. The exclusion criteria for the controls were the history of speech, language, neurological and hearing problems. Procedure In order to assess the phonological mean length of utterance, spontaneous speech utterances were elicited from each child for duration of 30 to 40 minutes. Samples consisted of minimum of 50 utterances. The experimenter served as a conversational partner and introduced the child to age appropriate toys and questions. The samples were obtained in an informal setting within the school premises for the control group and in the therapy premises for the clinical group. Audio recording was done using a portable Sony Recorder in a relatively quiet environment. The words were accepted for analysis according to the rules suggested by Ingram and Ingram which are mentioned in the table mentioned in appendix. The childrens production of utterances was narrow transcribed and PMLU was calculated for each child. For each word, the number of segments (consonants and vowels) as produced by the child was counted and summed with the number of correct consonants in a word. The sum of each word in all th e utterances of a single subject were totaled and divided by the number of words produced by the child to obtain the PMLU scores. Mann Whitney U test was administered to find out the significant differences between the means of both the groups. RESULTS: The results of the Mann Whitney U Test revealed a statistically significant difference between the means of pMLU scores across the group at p Group Statistics DISCUSSION: pMLU is a whole-word measure for phonological development and is used to investigate the difficulties if any in phonology and morphosyntax. The present study compared the pMLU of children with SLI in comparison with typically developing Kannada speaking children. The results of the study revealed that the pMLU scores for the children with SLI were lower in comparison to children with normal language development. This could be attributed to the increased number of incorrect consonants in the speech of clinical group when compared to the control group as these children were neutralizing the sound contrasts and also exhibiting syllable reduction strategies. Whether it is syllable structure reduction or sound contrast neutralization, it reduces the overall pMLU score. As children with SLI are inferior in the acquisition of segments as well as in their whole-word phonological proficiency than the typically developing children, phonological errors are reflected in the pMLU scores. Hence it can be concluded that pMLU reflects on the phonological errors. The results of the present study are in consonance with findings that the developments of phonology in children with SLI are much later in comparison to typically developing children (Balasbramanium Bhat, 2009) and also that children with phonological disorder are inferior in the acquisition of segments as well as in their whole-word phonological proficiency than the typically developing children (Prasad, Hossabetu, Balasubramanium Bhat 2010). Hence, pMLU can be used as an assessment tool for children with SLI as this provides an objective assessment tool in the evaluation process. The decrease in pMLU scores in the clinical group could also be due to the deficit in the use of morphosyntax as these children were having morphosyntactic errors. This in turn suggests that children with SLI are inferior in the acquisition of morphemic segments when compared to typically developing children. As this pMLU measure includes the number of segments in a word, pMLU can be used to indicate morphosyntactic abnormalities in children with SLI. This tool can also serve as an aid for monitoring the progress of a child when assessed pre and post therapeutically. CONCLUSION: The present study investigated pMLU in children with SLI in the age range of 4-6 years. The results revealed that children with SLI are inferior in the acquisition of segments including morphemes as well as in their whole-word phonological proficiency than the typically developing children. Hence, pMLU measure could be regarded as a yardstick for phonological and morphosyntactic development in children with SLI. REFERENCES: Aram, D. M., Ekelman, B. L., Nation, J. E. (1984). Preschoolers with language disorders: 10 years later. Journal of Speech and Hearing Research, 27, 232-244. Beitchman, J., Wilson, B., Brownlie, E. B., Walters, H., Lancee, W. (1996). Long-term consistency in speech/language profiles: I. Developmental and academic outcomes. Journal of the American Academy of Child and Adolescent Psychiatry, 35, 804-817. Bowen, C. (1998). Developmental phonological disorders: A practical guide for families and teachers. Melbourne: The Australian Council for Educational Research Ltd. Bishop, D. V. M. (1979). Comprehension in developmental language disorders. Developmental Medicine and Child Neurology 21, 225-38. Bishop, D. V. M. (1992a). Comprehension problems in children with specific language impairment: Literal and inferential meaning. Journal of Speech and Hearing Research, 35, 119-129. Helin, K., Makkonen, T., Kunnari, S. (2006). The Phonological mean length of utterance: the methodological challenge from cross linguistic perspectives. Journal of Child Language, 33, 179-190. ÂÂ  Hodson, B., Paden, E. (1991). Targetting Intelligible speech: a phonological approach to remediation. Austin TX: Pro-edition. Ingram, D. (2002). The measurement of whole-word productions. Journal of Child Language, 29, 713-733. Johnson, C. J., Beitchman, J. H., Young, A., Escobar, M., Atkinson, L., Wilson, B., Brownlie, E. B., Douglas, L., Tback, N., Lam, I., Wang, M. (1999). Fourteenyear follow-up of children with and without speech/language impairments: Speech/language stability and outcomes. Journal of Speech and Hearing Research, 42, 744-760. Lakkanna, S., Venkatesh, K., Bhat, J. (2007). Assessment of language development. Mangalore: Codeword processors. Leonard, L.B., mcgregor, K.K., Allen, G.D. (1992). Grammatical morphology and speechperception in children with specific language impairment. Journal of Speech and hearingresearch, 35, 1076-1085 Leonard, L. B. 1995 Functional categories in the grammars of children with Specific language impairment, Journal of Speech and Hearing Research, 38, 1270-83. Leonard, L. B. (1998). Children with specific language impairment. Cambridge, MA: Bradford. Lubert, N. (1981). Auditory perceptual impairments in children with specific language disorders: A review of the literature. Journal of Speech and Hearing Disorders, 46, 3-29. ÂÂ  Masterson, J., Kamhi, A. (1992). Linguistic interrelationships in school age children with and without language disorders. Journal of speech and Hearing Research, 35, 64-75. Olmstead, D. (1971). Out of the mouth of babes. The Hague: Mouton. Oetting, J., Horohov, J. (1997). Past tense marking in chldren with and without specific Language impairment. Journal of Speech and Hearing Research, 40, 62-74. Polite, J ., and Leonard, B. (2006). Finite verb morphology and phonological length in the speech of children with specific language impairment. Clinical Linguistics Phonetics, 20, 751-760. Radish, B., Jayashree, S. (2009). Phonological Mean Length of Utterance (Pmlu) in Kannada-Speaking Children. Language in India, 9, 489-502. Rice, M.L., Wexler, K., Cleave, P.L. (1995). Specific language impairment as a period of extended optional infinitive. Journal of Speech and Hearing Research, 38, 850-863. Rice, M. Wexler, K. (1996). A phenotype of specific language impairment. In M. Rice (Ed.), Toward a genetics of language, pp. 215-238. Mahwah, NJ: Lawrence Erlbaum Associates Inc. Stothard, S. E., Snowling, M., Bishop, D. V. M., Chipchase, B. B., Kaplan, C. A. (1998). Language impaired preschoolers: A follow-up into adolescence. Journal of Speech, Language and Hearing Research, 41, 407-418. ÂÂ  Templin, M. (1957). Certain language skills in children. Minneapolis, MN: University of Minnesota press. Taelman, H., Durieux, G., Gillis, S. (2005). Notes on Ingrams whole-word measures for phonological development. Journal of Child Language, 32, 391-405. Tomblin, J. B., Records, N. L., Buckwalter, P., Zhang, X., Smith, E., OBrien, M (1997). Prevalence of specific language impairment in kindergarten children. Journal of Speech Hearing Research, 40(6), 1245-1260. Van der Lely, H. K. J. Harris, M. 1990 Comprehension of reversible sentences in specifically language-impaired children. Journal of Speech and Hearing Disorders 55, 101-17. Van der Lely, H. K. J. 1996 Specifically language impaired and normally developing children: Verbal passive vs adjectival passive sentence interpretation, Lingua, 98, 243-72. Van der lely, H. K. J. Ullman M. T. (2001) Past tense morphology in specifically language impaired and normally developing children. Language and Cognitive Processes, 16: 177-217. Van der Lely, H. K. J. Battell, J. (2003) Wh-movement in childrenWith grammatical SLI: a test of the RDDR hypothesis, Language 79,153-81.