1.2 The Neurocognitive Profile of Williams Syndrome
Williams Syndrome - A Neurodevelopmental Disorder as Evidence for the dual Structure of the Human Language Faculty
2 The Study by Clahsen and Almazan
2.1.1 Subjects and Experiments
2.1.2 On the Linguistic Background
The Alternative Perspective
3 The Aspect of Development
3.1 Development and the Deep Level of Fractionation in WMS
Different language impairments have been argued to have the potential to reveal the modular structure of the human language faculty. While many linguists agree on the assumption, that the language faculty has a dual structure consisting of two separate systems the means to substantiate this allegation are quite diverse. In this work the focus is going to be on the debate wether Williams syndrome potentially can serve as evidence for modularity in language. Although until today there has been no absolute proof for an immediate connection between language and specific genes in Williams syndrome subjects (Karmiloff-Smith, A., 1998) certain aspects of the disorder seem to provide relevant information about language processing and performance errors. Besides Williams syndrome (WMS) investigations on Specific language impairment or Down syndrome are quite as common not least because they provide vital possibilities of comparison. Specific language impairment (SLI) is a form of developmental disorder and in this it is the most frequently diagnosed one. Despite numerous studies until today there is no gene associated with SLI (cf. Sonja C. Vernes et al., 2008). On the other hand Williams syndrome (WMS) “is a rare multi-system neurodevelopmental disorder with associated cardiac, craniofacial, and growth abnormalities, caused by a hemizygous microdeletion of some 28 genes on chromosome 7q11.23, including elastin (ELN) and LIM-kinase1 (LIMK1)”. The evolving problem now is the interconnection of two major factors. 1.) Proceeding from the assumption, that WMS is genetically caused whereas SLI is a developmental disorder, in how far is it reasonable to compare these two disorders at all? 2.) Secondly, are current WMS studies really suitable to describe the structure of the human language faculty? Thomas and Karmiloff-Smith state that “the detailed level of behavioural fractionations observed in these disorders goes beyond the possible contribution of genes and implicates the developmental process as a key contributor to the cognitive outcome” (Thomas and Karmiloff- Smith, 2005). This approach is of course a very challenging one because it tries to describe a problem which is not static. Whereas some studies primarily focus on comparing intact versus impaired modules, the ambitious attempt here is to “take serious account of the fact that the infant cortex passes from an initial state of high regional interconnectivity to a subsequent state of increasing specialization and localization of function” (Karmiloff-Smith, 2007). But it is also an attempt which considers the gradation within a particular disorder which is important too. Nevertheless, cross-syndrome comparisons have disclosed significantly different linguistic profiles and therefore remain useful to categorize and specify disorders in general. To narrow down the objective of this work however, it appears to be beneficial to outline the issue-area more precisely.
The structure of this work unfolds as follows. First, there is going to be a brief introduction into the cognitive profile of WMS with its remarkable peaks and valleys. Second, the basic argumentation of the study conducted by Clahsen and Almazan is going to be introduced. Since their conclusion targets to present WMS as evidence for the modular structure of the language faculty but dispenses the developmental aspects of the disorder it will be argued in a third section, that development plays a decisive role for the phenotypical outcome. This work is designed to introduce arguments which challenge the conclusion by Clahsen and Almazan in favour of a perspective, where development gains centre stage and which shows that fractionation in WMS “occurs on a much finer level than is plausible for the expression of genetic effects” (Thomas and Karmiloff-Smith, 2005). The specific profile of WMS alone is not suitable to describe the dual structure of the language faculty. The attempt to do so must inevitably lead to squalor of characteristics, which are eminently vital to gain a convincing insight into the fascinating linguistic profile of WMS.
1.2 The Neurocognitive Profile of Williams Syndrome
The growing interest in WMS in recent years has helped to uncover the fascinating profile of a disorder which is, above all, characterized by a discrepancy between language ability and IQ. People with WMS have an average IQ of approximately 60 (Mervis, 1990) and the frequency of occurrence is 1 in 20,000 births (Morris and Mervis, 1999). There is also a dissociation between spatial cognition (impaired) and face processing (spared). The uneven cognitive profile is shaped by poor visuospatial cognition in contrast to verbal cognition (E.K. Farran et. al., 2007) and therefore “subjects with WMS present a rare opportunity to study the separability of cognitive domains that normally develop together, and to characterize the trajectories of their development across the age span” (Bellugi et al., 2001). Due to the dissociations within and across cognitive domains the neurocognitive profile of WMS is often referred to as an unusual pattern of strengths and weaknesses (Bellugi et al., 2001). Especially the use of expressive linguistic devices is an index of the hypersocial nature and drive in WMS. The early development of the social nature of people with the disorder leads to their interest in engaging others. Various studies have shown the strong attraction to social interaction in children with WMS (Jones et al, 2001). It is often emphasized how the skilful use of language in situations of social engagement hides the fact, that children run into difficulties when it comes to language acquisition (Pipa, 2007). Hence, the onset of first words is delayed in children with the disorder and “it is not until WMS children reach school age that language typically becomes a relative strength” (Jones et al, 2001). Then again it is astonishing how they themselves perceive their impairment. “Their remarkable language provides a window into what it is like to have WMS in that it allows them to be able to explain eloquently what it feels like to be mentally retarded” (Bellugi and St. George, 2001). Whenever the phenotypic profile of WMS is examined it is important to distinguish between the behavioral and the cognitive phenotype here, since it is possible, “that equivalent behavioural scores camouflage very different cognitive processes” (Karmiloff-Smith, 2008). Furthermore, the analysis of the infant cognitive profile results in significant differences to the adult phenotypic outcome. Thus, it is difficult to examine “full developmental trajectories from infancy to adulthood at the level of cognitive processes rather than merely recording overt behaviour” (Karmiloff-Smith, 2008). While the social-affective understanding seems to be relatively proficient, the social-cognitive understanding of other minds is clearly impaired in WMS subjects. It is true, according to Karmiloff-Smith, that people with the disorder are often very loquacious but she also stresses the fact, that WMS is not the opposite of autism (Karmiloff-Smith, 2007). Compared to Down´s syndrome (DNS) for instance language and cognition in WMS subjects diverge over time. In older DNS individuals “linguistic abilities are far below those of WMS” (Bellugi et al., 2001) indicating an advantage in terms of linguistic development in WMS individuals. Starting out with significant delay the behavioural phenotype undergoes notable change across the first years of life which is not the case in DNS individuals. So, it becomes clear, that little in development is predetermined or fixed and we have to deliver ourselves from the widely held view, that the infant brain of WMS individuals is merely a juxtaposition of intact and impaired modules, or “segregated boxes” where damaged modules have no effect on any of the intact units (Karmiloff-Smith, 2008). On the contrary, we have to think of the initial state of the cortex as a composition of many interconnected units with initially brain regions which “are not domain specific but `domain relevant´” (Karmiloff-Smith, 2008). However, before we can get to the discussion of the controversy between genetically determined linguistic outcome (Clahsen and Almazan) and a highly developmental perspective (Karmiloff-Smith) it is important to introduce the procedure, the test environment (as far as possible) and the conclusions drawn by Clahsen and Almazan in their study.
2 The Study by Clahsen and Almazan (2001)
Now, proceeding from the assumption of a modular organization of the language faculty consisting of two systems at least, the objective of the study is to contribute empirical data which might support the argument for a dual structure of the human language faculty. The structure of this system is usually divided into two units: 1). The lexicon, representing a list of learned and stored entries/ words and their properties, whereas 2). the other unit is a computational system of abstract rules, which help to form larger expressions from the set of lexical entries (Radford, 2004). This categorization has been challenged frequently, especially by a model, which tries to represent language, as a connectionist network with associatively linked units. Therefore, relevant empirical evidence is inevitable. Supposedly, the promising source of evidence are selective impairments and dissociations found in language-disordered populations such as people with WMS.
For the study English-speaking subjects were examined in terms of plural formation and plurals inside compounds since the unusualness of the pattern of WMS eminently is regarded as an excluding mechanism by the authors. This is due to the aforementioned fact, that the syndrome unifies cognitive deficits and – according to Clahsen and Almazan - relative strength in language, which leads to the result, that in tests the subjects perform rather excellent on regular inflection and syntactic tasks whereas the performance on irregular inflection is worse. As subjects with Specific language impairment (SLI) reveal the opposite pattern, less convincing performance on syntactic tasks and regular inflection paired with good lexical skills, the authors consider results from previous investigations as suitable for reasons of comparison. Now, several authors who are generally critical about the question whether a fundamental dissociation between linguistic and non- linguistic skills in WMS individuals does exist at all, do acknowledge, that a verbal advantage over nonverbal intelligence can be observed. In their study, in order to create a linguistic profile, the authors favour a linguistic approach over the common studies where grammatical skills of WMS subjects are categorized by school grammar, omitting linguistic theory. The subject of analysis of the current investigation is plural formation and plurals inside compounds because the assumption is, that WMS subjects “are impaired in accessing subnode information” (Clahsen and Almazan, 2001). This assumption is partially also based on results from a previous study where past tense formation has been investigated, yet it remains unclear, wether it is the content of the sub-node, which is not always accessible or the link to the basic entry, or possibly even both. The analysis of plural formation and plurals-inside-compounds in WMS children eventually might reveal the interaction of different morphological processes.
- Quote paper
- Marcel Brauhardt (Author), 2010, Williams Syndrome in Psycholinguistics, Munich, GRIN Verlag, https://www.grin.com/document/152299