6. General discussion
6.4 Methodological considerations and future perspectives
The complement clause tasks required children to judge the truth value of a sentence uttered by a puppet. The main pitfall of the communication verb task was the insufficient amount of familiarisation items, and especially the lack of familiarisation items requiring the child to answer “no”. In the perception verb task, where additional familiarisation items had been added to control for children’s bias towards positive response, children with ASD still found had difficulty answering “no”. It could be that truth-value judgment tasks do not optimally reflect ASD children’s ability. Furthermore, taking into account what a puppet says requires skills in symbolic play, which is a documented difficulty in ASD children (Tager-Flusberg, 2000). Although no problems with the symbolic use of the puppet arose for our participants during administration of the test, it is possible that the symbolic aspect of the task interfered with the syntactic aspect.
Future tasks with ASD participants should take into account the need for an extensive familiarisation phase when using truth-value judgment tasks.
6.4.2 ToM tasks
It was mentioned in section 5.2.5 that the low-verbal false-belief task rendered results that were not expected given data from previous studies. The task may not show sufficient validity given the amount of possible response strategies.
It would have been interesting to conduct a detailed analysis of participants’ oral production in the picture-sequence task, as this may have provided insight into participants’ reasoning, namely whether they attributed a false belief to the protagonists.
Further research could delve into the distinction between implicit and explicit ToM measures, as all our tasks involved explicit ToM measures. Implicit ToM requires use of material that was not possible to use in participants’ homes (e.g. eye-tracking devices).
6.4.3 General considerations
Several issues can be raised concerning our population. Although they were all diagnosed as being on the Autism Spectrum in their childhood, diagnostic nomenclature varied greatly, including “psychosis”, “severe autism”, “Asperger’s” and “PDD”. Furthermore, parental reports of their child’s autism varied, and may have reflected an evolution of their child from when the diagnosis had been given. Although experimenters’ clinical training did not allow for it, it would have been ideal to conduct standardised clinical testing such as the ADOS or ADI-R to control for this.
Another issue related to the population is sample size. Although our sample was initially composed of 20 participants, which is a substantial number given the difficulties encountered to recruit participants, the inter-individual differences in age and cognitive abilities were such that a larger sample size would have increased the statistical power of analyses, possibly showing effects that we did not find for lack of statistical power.
Finally, our sample was constituted of 10 bilingual children. Some of the bilingual children had first been exposed to another language before their parents were advised to speak only in French to their child, even if their own dominant language was not French. Therefore, bilingualism may have affected participants’ responses. Namely, a link has been found between early bilingualism and a better ability in ToM (see for example Kovacs, 2009), which is of particular relevance to this study. Further analyses could be carried out to tease out the contribution of bilingualism on participants’ results.
A series of tasks measuring non-verbal IQ, memory and vocabulary were administered but not reported on in this thesis. It will therefore be of paramount importance to analyse data in light of results to these tasks, and to form several subgroups subsequently. In addition, individual participants’ answers across tasks would be interesting in order to identify response profiles.
Conclusion
This exploratory study aimed to examine ToM, syntax and ASD. Through various tasks studying ASD children’s comprehension of complex syntactic structures arising in the CP, it was suggested that children with ASD truncate the upper layers of the syntactic tree well beyond the expected age. Certain syntactic structures such as subject relatives, which are acquired at an early age in TD children, posed difficulty to the ASD group, even though ages ranged from 5 to 15, above the expected age for understanding SR in TD children.
Furthermore, the pattern of response indicated that children with ASD follow a developmental pattern that can be explained in part by Relativized Minimality (Rizzi, 1990, 2004) and Derivational Complexity (Jakubowicz, 2004, 2011). Although a subgroup of participants showed no effect of intervention or similarity, we interpreted this as a consequence of their poor results in all syntactic structures involving movement. The subgroup of children who performed better showed both an effect of movement and an effect of similarity, but no effect of intervention, contrary to what has been predicted by RM. We mention the possibility of a similarity effect in the absence of intervention, as proposed by cue-based parsing. Results could be analysed in light of data from the basic memory tasks such as the Corsi block-tapping test and the phonological loop test that we administered but did not analyse for this thesis. If correlations were to be found between results on the memory tests and the syntactic structures belonging to the higher levels of the syntactic complexity metric, this could allow to identify the kind of link that has been reported between working memory and syntax.
Several studies (e.g. Tager-Flusberg & Joseph 2005; Lind & Bowler 2009) have reported that ASD children’s ToM performance as measured by FB tasks is correlated with their correct understanding of sentential complements, in particular using verbs of communication. We delved into this by studying ASD children’s understanding of sentential complements using a verb of communication and a perception verb, which to our knowledge had never been tested in this population. Furthermore, we aimed to reduce the memory component of Tager-Flusberg and Joseph’s (2005) memory for complements task, by accompanying sentences with pictures. We then studied the link between understanding of sentential complements using a perception verb and understanding of ToM as measured by false belief tasks.
Contrary to the only previous study to our knowledge with TD children, which had studied the link between ToM and sentential complements with a perception verb (Poltrock, 2011), no significant correlation was found between these two measures. One explanation for this is
that the correlation is only found in TD children, and that ASD children benefit only from understanding of communication or cognition verbs in sentential complements in order to understand ToM. Similar tasks with these two types of verbs should be administered to test this hypothesis.
Contrary to our predictions, correlations were found between measures of ToM and understanding of different types of relative clauses and wh-questions. However, relative clauses have been found to correlate with ToM (Smith, Apperly and White, 2003), and wh-questions are part and parcel of traditional verbal FB tasks, which could explain this correlation It is suprising that a correlation was found between relative clause comprehension and ToM, but not between complement clause comprehension and ToM.
Indeed, it has been suggested that the characteristic of complement clauses that allows children with ASD to access ToM is embedding, thus explaining the correlations found with relative clauses in previous studies (Smith et al. 2003). Yet our results do not concur with this view, because if embedding were linked to ToM development, both complement clauses and relative clauses would correlate with false-belief tasks.
We expected ToM low-verbal measures to be independent from syntax in ASD children.
Indeed, if the ASD children who succeed on ToM false-belief tasks do so by using their knowledge of complex syntax (and in particular embedding) to understand the stories and the questions and to reason about them, then the low-verbal ToM measures should probably not be influenced by this knowledge. Our results go against this view, as correlations were found between relative clause and wh-question comprehension and all ToM measures, including the low-verbal content ones.
In sum, the present study has contributed to exploring the field of syntax in autism by examining structures that had not yet been studied in French-speaking children with ASD, and by combining several types of ToM measures to separate possible factors of success in FB tasks. Given the purported link between syntax and memory, analyses should be carried out to study this link in our population. In addition, it would be interesting to examine the relationship between Executive Functions such as inhibition, and ASD children’s ability to process complex syntax. Indeed, certain authors claim that Autism Spectrum Disorders are characterised by a core deficit in Executive Functions (e.g. Pennington & Ozonoff, 1996), which could explain the poor results in syntactic processing of complex structures, if Executive Functions influence syntax processing.
Future research with TD control children should allow to refine our knowledge of syntactic and ToM development in ASD. Furthermore, subgroups of ASD participants based on standardised vocabulary and/or IQ measures could allow to rule out a general cognitive delay across the board, and to establish finer profiles of ASD categories. Finally, subgroups based on specific diagnostic criteria could allow for identification of characteristic functioning in ASD children according to severity of the disorder.
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Appendix I : Syntax and truncation theory