- Email: [email protected]
Explaining grammatical difficulties in intellectual disabilities
Revista de Logopedia, Foniatría y Audiología (2013) 33, 64---68
Revista de
LOGOPEDIA, FONIATRÍA y AUDIOLOGÍA www.elsevier.es/logopedia
ORIGINAL ARTICLE
Explaining grammatical difficulties in intellectual disabilities夽 Jean A. Rondal University of Liège, Belgium Received 7 February 2013; accepted 21 April 2013 Available online 6 June 2013
KEYWORDS Intellectual disability; Down syndrome; Implicit memory; Morphosyntactical; Grammatical rehabilitation
Abstract Morphosyntactical difficulties are common in congenital syndromes of intellectual disabilities (ID). Explanations have been proposed in terms of global intellectual, explicit memory, and/or inadequacies in linguistic input that are questionable. I argue that the morphosyntactical limitations in the language development and functioning of these persons stem from a lesser ability in implicit learning, a type of learning arguably largely involved in grammatical development. This theoretical position has implications for grammatical rehabilitation. © 2013 AELFA. Published by Elsevier España, S.L. All rights reserved.
PALABRAS CLAVE
Explicación de las dificultades gramaticales en la discapacidad intelectual
Discapacidad intelectual; Síndrome de Down; Memoria implícita; Morfosintáctico; Rehabilitación gramatical
Resumen Las dificultades morfosintácticas son frecuentes en los síndromes congénitos de discapacidades intelectuales (DI). Se han propuesto explicaciones en términos de memoria global intelectual y explícita y/o deficiencias del input lingüístico, que son cuestionables. Yo sostengo que las limitaciones morfosintácticas en el desarrollo y funcionamiento lingüístico de estas personas se derivan de una menor capacidad de aprendizaje implícito, un tipo de aprendizaje que podría decirse que está ampliamente involucrado en el desarrollo gramatical. Esta posición teórica tiene implicaciones para la rehabilitación gramatical. © 2013 AELFA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
Introduction
夽 The rationale and the empirical arguments supporting the theoretical position exposed in this article are further developed in a paper entitled ‘‘Morphosyntactical difficulties and rehabilitation in persons with Down syndrome’’ (J.A. Rondal & G.M. Guazzo) to be published as a chapter of the International Review of Research in Developmental Disabilities (Vol. 41, R. Hodapp, guest volume editor), New York, Elsevier, 2012, in press. E-mail address: [email protected]
Difficulties in grammatical and particularly in morphosyntactic development and functioning are the rule rather than the exception in genetic congenital syndromes of ID (see Dykens, Hodapp, & Finucane, 2000; Murphy & Abbeduto, 2003; Rondal & Edwards, 1997; for reviews). Syntax is the language component in charge of organizing the expression sequentially. Morphology can be divided in stem morphology (the stable part of the word that can be a word on its own, e.g., love in lovely), derivational morphology (adding one or
0214-4603/$ – see front matter © 2013 AELFA. Published by Elsevier España, S.L. All rights reserved. http://dx.doi.org/10.1016/j.rlfa.2013.04.002
Explaining grammatical difficulties in intellectual disabilities several morphemes to a word stem to derive a new lexical category; e.g., lovely from love), and syntactic morphology --- the one which interests me here --- i.e., the particular morphemes that can be added to the stem for encoding one or several semantic dimensions such as number gender, time, and in flexional languages case or grammatical function; e.g., in Arabic, bis salâma, See you later (literally Until the peace with the morpheme --- a added to salâm (peace) as the object case --- accusative --- ruled by the preposition bis. The picture resulting from years of research on various syndromes of ID (cf. Rondal, 2009a) is one of an incomplete syntactic development characterized by a reduced use of articles, prepositions, auxiliaries, pronouns and conjunctions (the close classes of linguistics), little comprehension and use of the more complex types of sentences outside of semantic facilitation. However, at corresponding levels of mean length of utterance (MLU), word order in utterances does not differ in typically developing (TD) and children with ID. The latter also have particular difficulties with syntactic morphology (e.g., marking gender, number, person, and case, grammatical subject-verb agreement). No matter how common these difficulties are in persons with ID, no compelling explanation has been proposed so far.
Explaining grammatical difficulties in intellectual disabilities A seemingly obvious explanation of the difficulties mentioned is that they should be attributed to the general cognitive limitations characteristic of these syndromes (as assessed, for example, by measures of intellectual quotient or Piagetian stages of cognitive development). As commanding as such a type of explanation appears at first glance, it turns out to be wrong. Research shows that intellectual disability is not unavoidably tied to the existence of grammatical difficulties (syntactic and/or morphological). Specific data in that sense can be found in reports by Curtiss (1989), Yamada (1990), and Rondal (1995). Adolescents and adults with moderate to severe ID were found to exhibit normal or normal-like productive and receptive grammatical ability (morphological as well as syntactic) upon systematic psycholinguistic testing. This means that a cognitive ability situated within normal limits is not a necessary condition for standard grammatical development. I have suggested (Rondal, 2003) that the intellectual disability and the grammatical difficulties of standard persons with ID have different roots. The latter do not stem from limitations in general cognition, as proved a contrario by the atypical cases. They likely arise from a basic impairment in devoted brain structures. The persons with ID and atypically favorable grammatical ability escape this fate for reasons (so far undocumented) of positive phenotypic effects of genetic variation. Some time ago, it was theorized, based on inadequate data, that too simplified a linguistic input directed to the child with ID by the parents supplied a likely explanation for the language delays, and particularly the grammatical delay demonstrated by these children. Subsequent research (Gutmann & Rondal, 1979; Mahoney, 1988; Maurer & Sherrod, 1987; Petersen & Sherrod, 1982; Rondal &
65 Docquier, 2006; Rondal, 1978) showed, however, that at corresponding levels of language development (measured by MLU, for example) the language produced by the mothers of the children with ID does not differ from the language addressed by the mothers of children in normal development to their children. It follows that the responsibility for the grammatical delays and difficulties commonly observed in ID resides in the children and not in the language of the parents. Nowadays, short-term or working memory is almost automatically advocated in the technical literature a (partial) cause for any kind of language delay or problem whether in ID or specific language impairment. There is an important caveat, however. The way short-term memory is conceptualized in these sources is in its explicit, i.e., conscious and voluntary, dimension. It can be argued, however, that a very large part of children’s morphosyntactic learning proceeds in an implicit manner (see below). It follows that the whole literature on explicit memory is irrelevant, except perhaps regarding traditional language remediation whereby a conscious and voluntary learning interaction is established between therapist and child. It is still correct to posit causal memory problems in children with ID or developmental language disorders, but that has to concern the implicit memory system. The neural structures involved in implicit learning and memory (the so-called procedural system), as documented by research in brain hemodynamics, electrophysiology, and magnetoencephalography, are different from those regarding explicit learning and memory (the declarative system), which suggests a functional independence of the two systems. The former involve the frontal, parietal and superior temporal cortices (the perisylvian area on the left side overall), the left basal ganglia, and the right cerebellar structures, whereas the latter is rooted in a series of medial temporal lobe structures on both sides. They include the hippocampal and parahippocampal regions as well as the anterior cingulated cortex (Paradis, 2004). The procedural system plays a major role in learning and processing context-dependent relations between elements in real-time sequences. Learning occurs on an ongoing basis during multiple presentations of the elements. The learned product applies automatically to new corresponding or closely related surface material. I have suggested that most morphosyntactic learning proceeds in an implicit manner (Rondal, 2006, 2009b, 2010, 2011a, 2011b, 2011c). This learning, however, takes place within a pragmatical-semantical framework built early in life and gradually refined that is an instance of declarative knowledge and is developed accordingly. Also learning is helped by the now well-documented dynamic speech adaptation of parents and adults in general to the actual language levels of the language-learning children. Let me briefly specify the major characteristics of the model, before explaining why it is logically necessary and making clear what makes it different from both the behavioristic Skinnerian tradition and the present-day pragmatical orientation proposed by people like Tomasello, and then turning to specifying some the major rehabilitation implications of the theory. Syntactic patterning operating on the outcome of a pragmatic indexation framing a thematic semantical matrix
66 proceeds on line according to the sequential and distributional regularities of the tongue. Sentence surfaces contain the information (embodied in the relative word order combinations, function words, and syntactical morphemes) necessary to identify the speaker’s intent and retrieve the meaning intended. The editing mechanism controlling concord across sequences of words proceeds on the basis of proximal and distal associations. Recent work in neurolinguistics supports this proposal. For example, Dominey (1997), Dominey, Hoen, Blanc, and Lelekov-Boissard (2003), Dominey, Inui, and Hoen (2009) have specified a model of corticostriatal function in sentence comprehension based on sequential analysis. Simulations in artificial grammar learning show that internal structure in the strings of words can be encoded through repeated exposure and used to predict the next elements in the sentence. What is learned in sentence comprehension can then be used to regulate sentence production. Syntactical morphology reinforces cohesion within and between phrases, clauses and sentences. As suggested by Skinner (1957), the words inflected at the beginning of the sentence serve as discriminative flags reminding the speaker to operate cohesively with the following words. Given the arbitrary complexity of that part of the grammar, on the one hand, and the high speed of typical language production (approximately 3.3 words --- 12 to 15 phonemes --- per second; around 200 words per minute), on the other, it is not conceivable that syntactical morphological marking could proceed otherwise. Paradigmatic substitution exploiting isomorphic analogies (positional as well as semantical and pragmatical) in sentence surface structures largely contributes to the creativity of sentence production. The same mechanism is responsible for building up combinatorial categories corresponding but not equivalent to the formal categories of linguistics (see below). Corresponding privileges of occurrence implicitly noted by the speakers/hearers together with the semantical and pragmatical analogies mentioned above are sufficient for organizing these categories. Current production and comprehension is also accelerated by the recourse to ‘‘skeletal frames’’ (Skinner, 1957). Such frames are flexible patterned strings with determined slots where to insert relevant lexical forms. Zipf-Mandelbrot’s formula shows that a limited set of lexical units with a high frequency of occurrence accounts for the major part of the token distribution in any corpus of language (Manning & Schütze, 1999). The following indications confer to the above considerations a kind of deductive necessity. By far all the attempts in recent decades and years to explain grammatical development are based on the belief that the grammatical categories successfully exploited in linguistics to describe facts of the tongues are automatically relevant to account for the way bone and flesh people learn these categories and use them in production and understanding. As correctly implied by generative linguists, the linguistic formal (notions of noun, verb, adjective, etc.) and functional (notions of grammatical subject, complement, attribute, etc.) categories as well as a number of related grammatical notions, cannot be learned from the language input because they are abstract categories, except if one has at hand a number of grammatical representations which must be posited as
J.A. Rondal belonging to the human genotype as a property of species. The problem is that this sort of hypothesis has no support in molecular genetics, is highly implausible, and has not received any empirical support. In contrast, the existence of implicit knowledge regarding the sequential regulations and the syntactical morphological marking in sentences is quite obvious in any language speaker-hearer. As this sort of knowledge cannot correspond to the formal and functional linguistic categories, they must be of a learnable nature, hence the proposal above regarding the learned pragmaticalsemantical basis of combinatorial language and its direct translation in regulated sequences typical of the tongue. These sequences are learned implicitly from the statistical regularities of the input and subsequently automatized. Despite the above mentioned two ideas among the ones proposed by Skinner (1957), my theory diverges from his treatment of grammar in at least two major respects. First, Skinner refuses thematic semantics as well pragmatics on the ground of mentalism, the absolute sin in radical behaviorism. Hence, he finds himself in the uncomfortable position to be obliged to account for combinatorial language in terms of repertoires of utterances. This approach was criticized by Chomsky (1959) pointing out rightly that no natural language functions as a fixed repertoire of utterances. Second, and for the same reason, Skinner could not envisage the paradigmatic substitution principle that I have deemed necessary to account for the creativity of language evidenced by the speakers in sentence production. A point of view at 180 degrees from Skinner’s proposal, so to speak, is the one of Tomasello (2003). Influenced by the pragmatic movement in anthropology, this author postulates that the morphosyntactic regulations of language follow naturally in some way (undefined) from the semantical and overall the pragmatical framework pre-existing to sentence production, as a sort of communicative necessity. This is highly unlikely. First, there is nothing in the pragmatical framework that says even minimally how sentences should be organized morphosyntactically. It may be postulated that basic pragmatical organization is universal in human beings. Yet, as we know, the morphosyntax of the tongues can differ widely. The same is true for semantics. Thematic semantical relations are unordered by definition. Morphosyntax, on the contrary is patterned sequentially with a high degree of precision. The morphosyntactical shortcomings documented in standard individuals with ID are not explicable either in pragmatical or thematic semantical terms although delays in these developments contribute to a later onset of grammatical development. At corresponding mental ages (MA), children and adolescents with Down syndrome (DS) and their TD peers do not differ markedly in conversational skills and illocutory acts. At corresponding MLU or MA, children with DS produce and understand the same set of thematic semantical relations as TD peers (Rondal & Edwards, 1997). Morphosyntactical shortcomings in persons with ID are genuinely grammatical in nature. Children with DS experience particular difficulties in translating pragmatical and thematic semantical indications in the sequential and distributional morphosyntactical patterns of the tongue. Nonlinguistic processing deficits arising from the pathological condition may limit procedural implicit learning. These
Explaining grammatical difficulties in intellectual disabilities deficits include attention difficulties, slowed processing rates, and global capacity limitation related to the overall volumetric brain reduction observed in DS and affecting neuronal connectivity (Sporns, 2011). Anomalies of brain structures devoted to procedural implicit memory (short- and longer-term) are involved in the grammatical productive and receptive difficulties usually observed in persons with ID. Little information is on implicit memory in people with ID. It is likely that children with ID do not dispose of fully developed abilities in implicit procedural learning and memory correlates for morphosyntax. Recent autopsy observations, volumetric magnetic resonance imaging, and voxel-based morphometry (Vicari & Menghini, 2011) confirm the existence in individuals with DS of a reduction in overall brain volume, with a disproportionately smaller volume in the frontal, temporal, and cerebellar regions contrasting with a relatively preserved volume of subcortical areas and posterior (parietal and occipital) cortical gray matter. Vicari and Menghini (2011) suggest that the better ability of persons with DS in visuo-spatial procedural implicit learning may be related to a preserved functioning of the basal ganglia despite structural abnormalities in cerebellar areas. Regarding morphosyntactical learning, the cerebellum density reduction can contaminate procedural implicit learning despite a possible preservation of the subcortical structures. Additionally, as the basal ganglia project onto the frontal cortical area, the underdevelopment of Broca area in standard individuals with DS could also act as limiting factor on implicit grammatical learning.
Rehabilitation perspectives Morphosyntactical rehabilitation must be part of a general neurocognitive rehabilitation (cf. Rondal, Perera, & Spiker, 2011). Within language, clinical activities must be directed toward improving the development of the various subcomponents of the system. Children with ID may require more extensive exposure and practice to develop a functional procedural implicit memory in the case of morphosyntax than TD children of the same chronological and even mental ages. In order to be maximally efficient, an intervention aiming at improving morphosyntactical development should follow several principles. It should be practiced in everyday speech avoiding appealing to the formal and functional categories, abstract rules, and other metalinguistic language. It should privilege a direct mapping of the pragmatical/thematic semantical framework onto the sequential and distributional patterns of lexemes and syntactical morphemes characteristic of the tongue. The learning environment should reduce the demands bearing on the procedural system, breaking down complex sequences into component parts and recombining them gradually in larger units. The rate of speech addressed to the child with ID should be reduced and the natural pauses between phrases and clauses slightly exaggerated to stress sentence surface organization. The construction of paradigmatic repertoires should be favored through analogical substitutions of lexical groups, phrases and clauses. And the input should be delivered in such a way as to stress the distribution of the syntactical morphemes in the sentences.
67
Conflict of interest The authors declare no conflict of interest.
References Chomsky, N. (1959). Review of Verbal behavior by B.F. Skinner. Language, 35, 26---58. Curtiss, S. (1989). Abnormal language acquisition and the modularity of language. In F. Newmeyer (Ed.), Linguistics: The Cambridge survey (Vol. 2) (pp. 96---116). Cambridge, UK: Cambridge University Press. Dominey, P. (1997). An anatomically structured sensory-motor sequence learning system displays some general linguistic capacities. Brain and Language, 59, 50---75. Dominey, P., Hoen, M., Blanc, J. M., & Lelekov-Boissard, T. (2003). Neurological basis of language and sequential cognition: Evidence from simulation, aphasia, and ERP studies. Brain and Language, 86(2), 207---225. Dominey, P., Inui, T., & Hoen, M. (2009). Neural network processing of natural language: II. Towards a unified model of corticostriatal function in learning sentence comprehension and non-linguistic sequencing. Brain and Language, 109(2---3), 80---92. Dykens, E., Hodapp, R., & Finucane, B. (2000). Genetics and mental retardation. Baltimore, MD: Brookes. Gutmann, A., & Rondal, J. A. (1979). Verbal operants in mothers’s speech to nonretarded and Down’s syndrome children matched for linguistic level. American Journal of Mental Deficiency, 83, 446---452. Mahoney, G. (1988). Maternal communicative style with mentally retarded children. American Journal of Mental Deficiency, 92, 352---359. Manning, C., & Schütze, H. (1999). Foundations of statistical natural language processing. Cambridge, MA: MIT Press. Maurer, H., & Sherrod, K. (1987). Context of directives given to young children with Down’s syndrome and nonretarded children. American Journal of Mental Deficiency, 91, 579---590. Murphy, M., & Abbeduto, L. (2003). Language and communication in Fragile X syndrome. In L. Abbeduto (Ed.), International review of research in mental retardation (Vol. 27) Language and communication in mental retardation (pp. 83---119). New York: Academic Press. Paradis, M. (2004). A neurolinguistic theory of bilingualism. Amsterdam: Benjamins. Petersen, G., & Sherrod, K. (1982). Relationships of maternal language to developmental and language delay of children. American Journal of Mental Deficiency, 86, 391---398. Rondal, J. A. (1978). Maternal speech to normal and Down’s syndrome children matched for mean length of utterance. In C. Meyers (Ed.), Quality of life in the severely and profoundly retarded people: Research foundations for improvement (pp. 193---265). Washington, DC: American Association on Mental Deficiency. Rondal, J. A. (1995). Exceptional language in Down syndrome. In Implication for the cognition---language relationship. New York: Cambridge University Press. Rondal, J. A. (2003). Atypical language development in individuals with mental retardation: Theoretical implications. In L. Abbeduto (Ed.), Research in Mental Retardation (Vol. 27) (pp. 281---308). New York: Academic Press. Rondal, J. A. (2006). Expliquer l’acquisition du langage. Caveats et perspectives. Mardaga: Hayen (Sprimont), Belgique. Rondal, J. A. (2009a). Psycholinguistique du handicap mental. Marseille: Solal. Rondal, J. A. (2009b). La adquisicion del lenguaje. Teoria y bases (Vol. XXI) Barcelona: Ars Medica.
68 Rondal, J. A. (2010). Morphosyntactic learning: A neurobehavioral perspective. The Behavior Analyst Today, 11(2), 105---116. Rondal, J. A. (2011a). L’apprentissage implicite du langage. Mardaga: Wavre, Belgique. Rondal, J. A. (2011b). La morfosintaxis de los enunciados: categorias lingüisticas de la profundidad a la superficie o regulaciones en linea sobre base pragmatico-semantica? Revista de logopedia, Foniatria y Audiologia, 31(2), 57---64. Rondal, J. A. (2011c). L’organisation interne des énoncés: un ensemble de régulations analogiques apprises implicitement? Développements, 8, 55---63. Rondal, J. A., & Docquier, L. (2006). Maternal speech to Down syndrome children. An update. Journal of Speech-Language pathology and Applied Behavior Analysis, 1, 218---227. Rondal, J. A., & Edwards, S. (1997). Language in mental retardation. London, UK: Whurr.
J.A. Rondal Rondal, J. A., Perera, J., & Spiker, D. (2011). Neurocognitive rehabilitation in Down syndrome. In The early years. Cambridge, UK: Cambridge University Press. Skinner, B. F. (1957). Verbal behavior. Englewood Cliffs, NJ: Prentice-Hall. Sporns, O. (2011). Networks of the brain. Cambridge, MA: MIT Press. Tomasello, M. (2003). Constructing a language. Cambridge, MA: Harvard University Press. Vicari, S., & Menghini, D. (2011). Memory development and learning. In J. A. Rondal, J. Perera, & D. Spiker (Eds.), Neurocognitive rehabilitation in Down syndrome. The early years (pp. 164---174). Cambridge, UK: Cambridge University Press. Yamada, J. (1990). Laura: A case for the modularity of language. Cambridge, MA: MIT Press.
Revista de
LOGOPEDIA, FONIATRÍA y AUDIOLOGÍA www.elsevier.es/logopedia
ORIGINAL ARTICLE
Explaining grammatical difficulties in intellectual disabilities夽 Jean A. Rondal University of Liège, Belgium Received 7 February 2013; accepted 21 April 2013 Available online 6 June 2013
KEYWORDS Intellectual disability; Down syndrome; Implicit memory; Morphosyntactical; Grammatical rehabilitation
Abstract Morphosyntactical difficulties are common in congenital syndromes of intellectual disabilities (ID). Explanations have been proposed in terms of global intellectual, explicit memory, and/or inadequacies in linguistic input that are questionable. I argue that the morphosyntactical limitations in the language development and functioning of these persons stem from a lesser ability in implicit learning, a type of learning arguably largely involved in grammatical development. This theoretical position has implications for grammatical rehabilitation. © 2013 AELFA. Published by Elsevier España, S.L. All rights reserved.
PALABRAS CLAVE
Explicación de las dificultades gramaticales en la discapacidad intelectual
Discapacidad intelectual; Síndrome de Down; Memoria implícita; Morfosintáctico; Rehabilitación gramatical
Resumen Las dificultades morfosintácticas son frecuentes en los síndromes congénitos de discapacidades intelectuales (DI). Se han propuesto explicaciones en términos de memoria global intelectual y explícita y/o deficiencias del input lingüístico, que son cuestionables. Yo sostengo que las limitaciones morfosintácticas en el desarrollo y funcionamiento lingüístico de estas personas se derivan de una menor capacidad de aprendizaje implícito, un tipo de aprendizaje que podría decirse que está ampliamente involucrado en el desarrollo gramatical. Esta posición teórica tiene implicaciones para la rehabilitación gramatical. © 2013 AELFA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
Introduction
夽 The rationale and the empirical arguments supporting the theoretical position exposed in this article are further developed in a paper entitled ‘‘Morphosyntactical difficulties and rehabilitation in persons with Down syndrome’’ (J.A. Rondal & G.M. Guazzo) to be published as a chapter of the International Review of Research in Developmental Disabilities (Vol. 41, R. Hodapp, guest volume editor), New York, Elsevier, 2012, in press. E-mail address: [email protected]
Difficulties in grammatical and particularly in morphosyntactic development and functioning are the rule rather than the exception in genetic congenital syndromes of ID (see Dykens, Hodapp, & Finucane, 2000; Murphy & Abbeduto, 2003; Rondal & Edwards, 1997; for reviews). Syntax is the language component in charge of organizing the expression sequentially. Morphology can be divided in stem morphology (the stable part of the word that can be a word on its own, e.g., love in lovely), derivational morphology (adding one or
0214-4603/$ – see front matter © 2013 AELFA. Published by Elsevier España, S.L. All rights reserved. http://dx.doi.org/10.1016/j.rlfa.2013.04.002
Explaining grammatical difficulties in intellectual disabilities several morphemes to a word stem to derive a new lexical category; e.g., lovely from love), and syntactic morphology --- the one which interests me here --- i.e., the particular morphemes that can be added to the stem for encoding one or several semantic dimensions such as number gender, time, and in flexional languages case or grammatical function; e.g., in Arabic, bis salâma, See you later (literally Until the peace with the morpheme --- a added to salâm (peace) as the object case --- accusative --- ruled by the preposition bis. The picture resulting from years of research on various syndromes of ID (cf. Rondal, 2009a) is one of an incomplete syntactic development characterized by a reduced use of articles, prepositions, auxiliaries, pronouns and conjunctions (the close classes of linguistics), little comprehension and use of the more complex types of sentences outside of semantic facilitation. However, at corresponding levels of mean length of utterance (MLU), word order in utterances does not differ in typically developing (TD) and children with ID. The latter also have particular difficulties with syntactic morphology (e.g., marking gender, number, person, and case, grammatical subject-verb agreement). No matter how common these difficulties are in persons with ID, no compelling explanation has been proposed so far.
Explaining grammatical difficulties in intellectual disabilities A seemingly obvious explanation of the difficulties mentioned is that they should be attributed to the general cognitive limitations characteristic of these syndromes (as assessed, for example, by measures of intellectual quotient or Piagetian stages of cognitive development). As commanding as such a type of explanation appears at first glance, it turns out to be wrong. Research shows that intellectual disability is not unavoidably tied to the existence of grammatical difficulties (syntactic and/or morphological). Specific data in that sense can be found in reports by Curtiss (1989), Yamada (1990), and Rondal (1995). Adolescents and adults with moderate to severe ID were found to exhibit normal or normal-like productive and receptive grammatical ability (morphological as well as syntactic) upon systematic psycholinguistic testing. This means that a cognitive ability situated within normal limits is not a necessary condition for standard grammatical development. I have suggested (Rondal, 2003) that the intellectual disability and the grammatical difficulties of standard persons with ID have different roots. The latter do not stem from limitations in general cognition, as proved a contrario by the atypical cases. They likely arise from a basic impairment in devoted brain structures. The persons with ID and atypically favorable grammatical ability escape this fate for reasons (so far undocumented) of positive phenotypic effects of genetic variation. Some time ago, it was theorized, based on inadequate data, that too simplified a linguistic input directed to the child with ID by the parents supplied a likely explanation for the language delays, and particularly the grammatical delay demonstrated by these children. Subsequent research (Gutmann & Rondal, 1979; Mahoney, 1988; Maurer & Sherrod, 1987; Petersen & Sherrod, 1982; Rondal &
65 Docquier, 2006; Rondal, 1978) showed, however, that at corresponding levels of language development (measured by MLU, for example) the language produced by the mothers of the children with ID does not differ from the language addressed by the mothers of children in normal development to their children. It follows that the responsibility for the grammatical delays and difficulties commonly observed in ID resides in the children and not in the language of the parents. Nowadays, short-term or working memory is almost automatically advocated in the technical literature a (partial) cause for any kind of language delay or problem whether in ID or specific language impairment. There is an important caveat, however. The way short-term memory is conceptualized in these sources is in its explicit, i.e., conscious and voluntary, dimension. It can be argued, however, that a very large part of children’s morphosyntactic learning proceeds in an implicit manner (see below). It follows that the whole literature on explicit memory is irrelevant, except perhaps regarding traditional language remediation whereby a conscious and voluntary learning interaction is established between therapist and child. It is still correct to posit causal memory problems in children with ID or developmental language disorders, but that has to concern the implicit memory system. The neural structures involved in implicit learning and memory (the so-called procedural system), as documented by research in brain hemodynamics, electrophysiology, and magnetoencephalography, are different from those regarding explicit learning and memory (the declarative system), which suggests a functional independence of the two systems. The former involve the frontal, parietal and superior temporal cortices (the perisylvian area on the left side overall), the left basal ganglia, and the right cerebellar structures, whereas the latter is rooted in a series of medial temporal lobe structures on both sides. They include the hippocampal and parahippocampal regions as well as the anterior cingulated cortex (Paradis, 2004). The procedural system plays a major role in learning and processing context-dependent relations between elements in real-time sequences. Learning occurs on an ongoing basis during multiple presentations of the elements. The learned product applies automatically to new corresponding or closely related surface material. I have suggested that most morphosyntactic learning proceeds in an implicit manner (Rondal, 2006, 2009b, 2010, 2011a, 2011b, 2011c). This learning, however, takes place within a pragmatical-semantical framework built early in life and gradually refined that is an instance of declarative knowledge and is developed accordingly. Also learning is helped by the now well-documented dynamic speech adaptation of parents and adults in general to the actual language levels of the language-learning children. Let me briefly specify the major characteristics of the model, before explaining why it is logically necessary and making clear what makes it different from both the behavioristic Skinnerian tradition and the present-day pragmatical orientation proposed by people like Tomasello, and then turning to specifying some the major rehabilitation implications of the theory. Syntactic patterning operating on the outcome of a pragmatic indexation framing a thematic semantical matrix
66 proceeds on line according to the sequential and distributional regularities of the tongue. Sentence surfaces contain the information (embodied in the relative word order combinations, function words, and syntactical morphemes) necessary to identify the speaker’s intent and retrieve the meaning intended. The editing mechanism controlling concord across sequences of words proceeds on the basis of proximal and distal associations. Recent work in neurolinguistics supports this proposal. For example, Dominey (1997), Dominey, Hoen, Blanc, and Lelekov-Boissard (2003), Dominey, Inui, and Hoen (2009) have specified a model of corticostriatal function in sentence comprehension based on sequential analysis. Simulations in artificial grammar learning show that internal structure in the strings of words can be encoded through repeated exposure and used to predict the next elements in the sentence. What is learned in sentence comprehension can then be used to regulate sentence production. Syntactical morphology reinforces cohesion within and between phrases, clauses and sentences. As suggested by Skinner (1957), the words inflected at the beginning of the sentence serve as discriminative flags reminding the speaker to operate cohesively with the following words. Given the arbitrary complexity of that part of the grammar, on the one hand, and the high speed of typical language production (approximately 3.3 words --- 12 to 15 phonemes --- per second; around 200 words per minute), on the other, it is not conceivable that syntactical morphological marking could proceed otherwise. Paradigmatic substitution exploiting isomorphic analogies (positional as well as semantical and pragmatical) in sentence surface structures largely contributes to the creativity of sentence production. The same mechanism is responsible for building up combinatorial categories corresponding but not equivalent to the formal categories of linguistics (see below). Corresponding privileges of occurrence implicitly noted by the speakers/hearers together with the semantical and pragmatical analogies mentioned above are sufficient for organizing these categories. Current production and comprehension is also accelerated by the recourse to ‘‘skeletal frames’’ (Skinner, 1957). Such frames are flexible patterned strings with determined slots where to insert relevant lexical forms. Zipf-Mandelbrot’s formula shows that a limited set of lexical units with a high frequency of occurrence accounts for the major part of the token distribution in any corpus of language (Manning & Schütze, 1999). The following indications confer to the above considerations a kind of deductive necessity. By far all the attempts in recent decades and years to explain grammatical development are based on the belief that the grammatical categories successfully exploited in linguistics to describe facts of the tongues are automatically relevant to account for the way bone and flesh people learn these categories and use them in production and understanding. As correctly implied by generative linguists, the linguistic formal (notions of noun, verb, adjective, etc.) and functional (notions of grammatical subject, complement, attribute, etc.) categories as well as a number of related grammatical notions, cannot be learned from the language input because they are abstract categories, except if one has at hand a number of grammatical representations which must be posited as
J.A. Rondal belonging to the human genotype as a property of species. The problem is that this sort of hypothesis has no support in molecular genetics, is highly implausible, and has not received any empirical support. In contrast, the existence of implicit knowledge regarding the sequential regulations and the syntactical morphological marking in sentences is quite obvious in any language speaker-hearer. As this sort of knowledge cannot correspond to the formal and functional linguistic categories, they must be of a learnable nature, hence the proposal above regarding the learned pragmaticalsemantical basis of combinatorial language and its direct translation in regulated sequences typical of the tongue. These sequences are learned implicitly from the statistical regularities of the input and subsequently automatized. Despite the above mentioned two ideas among the ones proposed by Skinner (1957), my theory diverges from his treatment of grammar in at least two major respects. First, Skinner refuses thematic semantics as well pragmatics on the ground of mentalism, the absolute sin in radical behaviorism. Hence, he finds himself in the uncomfortable position to be obliged to account for combinatorial language in terms of repertoires of utterances. This approach was criticized by Chomsky (1959) pointing out rightly that no natural language functions as a fixed repertoire of utterances. Second, and for the same reason, Skinner could not envisage the paradigmatic substitution principle that I have deemed necessary to account for the creativity of language evidenced by the speakers in sentence production. A point of view at 180 degrees from Skinner’s proposal, so to speak, is the one of Tomasello (2003). Influenced by the pragmatic movement in anthropology, this author postulates that the morphosyntactic regulations of language follow naturally in some way (undefined) from the semantical and overall the pragmatical framework pre-existing to sentence production, as a sort of communicative necessity. This is highly unlikely. First, there is nothing in the pragmatical framework that says even minimally how sentences should be organized morphosyntactically. It may be postulated that basic pragmatical organization is universal in human beings. Yet, as we know, the morphosyntax of the tongues can differ widely. The same is true for semantics. Thematic semantical relations are unordered by definition. Morphosyntax, on the contrary is patterned sequentially with a high degree of precision. The morphosyntactical shortcomings documented in standard individuals with ID are not explicable either in pragmatical or thematic semantical terms although delays in these developments contribute to a later onset of grammatical development. At corresponding mental ages (MA), children and adolescents with Down syndrome (DS) and their TD peers do not differ markedly in conversational skills and illocutory acts. At corresponding MLU or MA, children with DS produce and understand the same set of thematic semantical relations as TD peers (Rondal & Edwards, 1997). Morphosyntactical shortcomings in persons with ID are genuinely grammatical in nature. Children with DS experience particular difficulties in translating pragmatical and thematic semantical indications in the sequential and distributional morphosyntactical patterns of the tongue. Nonlinguistic processing deficits arising from the pathological condition may limit procedural implicit learning. These
Explaining grammatical difficulties in intellectual disabilities deficits include attention difficulties, slowed processing rates, and global capacity limitation related to the overall volumetric brain reduction observed in DS and affecting neuronal connectivity (Sporns, 2011). Anomalies of brain structures devoted to procedural implicit memory (short- and longer-term) are involved in the grammatical productive and receptive difficulties usually observed in persons with ID. Little information is on implicit memory in people with ID. It is likely that children with ID do not dispose of fully developed abilities in implicit procedural learning and memory correlates for morphosyntax. Recent autopsy observations, volumetric magnetic resonance imaging, and voxel-based morphometry (Vicari & Menghini, 2011) confirm the existence in individuals with DS of a reduction in overall brain volume, with a disproportionately smaller volume in the frontal, temporal, and cerebellar regions contrasting with a relatively preserved volume of subcortical areas and posterior (parietal and occipital) cortical gray matter. Vicari and Menghini (2011) suggest that the better ability of persons with DS in visuo-spatial procedural implicit learning may be related to a preserved functioning of the basal ganglia despite structural abnormalities in cerebellar areas. Regarding morphosyntactical learning, the cerebellum density reduction can contaminate procedural implicit learning despite a possible preservation of the subcortical structures. Additionally, as the basal ganglia project onto the frontal cortical area, the underdevelopment of Broca area in standard individuals with DS could also act as limiting factor on implicit grammatical learning.
Rehabilitation perspectives Morphosyntactical rehabilitation must be part of a general neurocognitive rehabilitation (cf. Rondal, Perera, & Spiker, 2011). Within language, clinical activities must be directed toward improving the development of the various subcomponents of the system. Children with ID may require more extensive exposure and practice to develop a functional procedural implicit memory in the case of morphosyntax than TD children of the same chronological and even mental ages. In order to be maximally efficient, an intervention aiming at improving morphosyntactical development should follow several principles. It should be practiced in everyday speech avoiding appealing to the formal and functional categories, abstract rules, and other metalinguistic language. It should privilege a direct mapping of the pragmatical/thematic semantical framework onto the sequential and distributional patterns of lexemes and syntactical morphemes characteristic of the tongue. The learning environment should reduce the demands bearing on the procedural system, breaking down complex sequences into component parts and recombining them gradually in larger units. The rate of speech addressed to the child with ID should be reduced and the natural pauses between phrases and clauses slightly exaggerated to stress sentence surface organization. The construction of paradigmatic repertoires should be favored through analogical substitutions of lexical groups, phrases and clauses. And the input should be delivered in such a way as to stress the distribution of the syntactical morphemes in the sentences.
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Conflict of interest The authors declare no conflict of interest.
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