Áreas Relativas

8.5 How Do These Findings Impact on Other Theoretical Explanations of

ASD?

8.5.1 Relational Processing

As discussed in Chapter 1, episodic Remembering involves the self engaging in mental time travel (Tulving, 2005), and the re-creation of the spatial and temporal context of a previously experienced episode. In this way episodic Remembering requires the binding together of elements of an experienced episode (Chalfonte & Johnson, 1996), for example, the binding of the place and time of an event. Episodic memory shares many common attributes with Relational Processing (see Chapter 1). Therefore the findings from Experiments 1 to 5 can also be applied to the theory of impaired Relational Processing in ASD (Bowler et al., 2008b).

The DRM Remember/Know paradigm used for Experiment 3 confirmed that individuals with ASD were just as susceptible to memory illusions as the TD group. These findings provide evidence to suggest that individuals with ASD were aware of the semantic and associative relations of the word lists at encoding. However the results of Experiment 5 provide evidence to suggest that the Relational Processing deficit may also extend to encoding processes. For that Experiment, participants were asked to study item and colour combinations, and were tested for, (1) single feature recognition (i.e., item recognition) and (2) combined feature recognition (i.e.,

item and colour). The results demonstrated marginally diminished overall recognition during both item alone and, item plus colour combinations. These findings suggest that individuals with ASD find tasks that involve encoding combinations of features more difficult compared to single features. However, as the study was not designed to test whether single versus multiple feature encoding instructions effect overall recognition in ASD, there was no control condition (i.e., a condition with instructions to memorise single features of the items was not included). To test this, the study could be repeated with a manipulation of study phase instructions. In one condition, participants could be asked to memorise both the item and its presentation colour, whilst in the second condition participants could be asked to memorise either the item or its colour (Red or Blue). The findings from this study would help to clarify whether instructions to memorise multiple features of a studied stimuli, present a particular difficulty for individuals with ASD.

As we have seen, individuals with ASD also show diminished Old-New effects (for word stimuli; Experiment 1, 3, as well as for nameable picture stimuli; Item recognition and late anterior effects in Experiment 5) when verbal labels are involved and no impairment on tasks where verbal labels are not involved (Experiment 4). It is possible to speculate that this pattern of findings results from more of a general impairment with binding the stimulus (line drawing or word) with its verbal label. The suggestion of a Relational Processing deficit for stimulus - word label pairings is in line with the previous suggestion that individuals with ASD experience difficulties with processing combinations of features (line-drawing plus colour of presentation, observed in Experiment 5), and is in line with the observations reported in Experiments 1 and 3 of this thesis, where TD individuals may have been using a word-labelling strategy to memorise the word lists. Future studies designed to investigate Relational Processing deficits in ASD (particularly at encoding) would help to elucidate these observations (for example, see Gaigg et al., 2008; Gaigg, Bowler, Ecker, Calvo-Merino & Murphy, 2010).

8.5.2 Executive Functioning

Individuals with ASD demonstrate impairments in EF (see Hill 2004b for a review) which may be related to the diminished reports of episodic memory we observe in this population. This is because episodic memory shares some characteristic task requirements with tests of EF. For example, the phenomenological experience of episodic memory (autonoetic conscious awareness) involves shifting attention from the current perspective to a past perspective, in order to recall the spatial and temporal context of the episode. The ability to inhibit a response and to shift attention is also measured by many higher order cognitive functions (EF tasks) such as planning, working memory, mental flexibility (shifting set), inhibition of response, generativity and action monitoring (Rabbitt, 1997). Taken together this literature suggests that impairments in

episodic memory may be linked to the deficits we observe in EF ability in ASD.

It is possible to speculate about the nature of the findings from Experiments 1 to 5, in relation to recent findings in tests of EF in ASD. The research presented in section 8.4 demonstrates that individuals with ASD are less likely to use verbal strategies (or inner speech) to aid recognition. This resonates with studies that have provided evidence to suggest that some aspects of EF depend on verbal thinking in TD individuals (Baldo, Dronkers, Wilking, Ludy, Raskin, et al., 2005). Moreover, in a study by Williams et al., (in press), (see p. 161), in which participants with and without a diagnosis of ASD were asked to complete the Tower of London puzzle, just over one third of individuals with ASD but almost 90% of the TD group were negatively affected by an articulatory suppression condition. The authors concluded that unlike the TD group, the ASD group were less likely to verbally mediate their planning on the task (i.e., use inner speech). They made this conclusion on the basis that if planning in the ASD group was verbally mediated, the ASD group would have shown a similar degree of performance decline the TD group under articulatory suppression conditions. Furthermore the authors observed that the extent to which articulatory suppression negatively affected the ASD group’s performance in the task was correlated with the severity of communication difficulty individuals experienced. This finding provides strong evidence to suggest that verbal mediation and the use of inner speech is significantly less relied upon during planning tasks in ASD compared to TD individuals. Similar findings have been observed in tests of task-switching under articulatory suppression conditions in ASD (see p.172). Furthermore, planning in the Tower of London task is akin to episodic future thinking, which is thought to be mediated by the same neural structures as episodic memory (Suddendorf & Corballis, 1997; Wheeler et al., 1997; Buckner & Carroll, 2007; Lind & Bowler, 2010).

Both episodic memory and EF tasks are likely to be verbally mediated for TD individuals, and there is accumulating evidence to suggest that this is less likely to be the case for individuals with ASD. It is also possible that verbal thinking may atypically mediate recognition memory in ASD.

8.5.3 ToM Deficit

As discussed in Chapter 1, Perner’s (2000) account of metarepresentational ability suggests that metarepresentation enables both an understanding of false belief and of episodic Remembering. According to Perner and Ruffman (1995) this ability emerges between the ages of three to six years of age, prior to which children do not understand what experience is, and in turn, cannot reflect upon the perceptual origin of their knowledge. It is only after children are able to encode events as experienced that they can experience episodic Remembering. From this

perspective, it is possible to speculate that poor performance on ToM measures (e.g., false belief tasks, Perner & Wimmer, 1985, see Chapter 1) would suggest impaired episodic Memory. However, this explanation for the diminished Remember judgements observed during behavioural tests of episodic Memory in ASD is not complete. This is because individuals with ASD do not always fail ToM tests (see Bowler, 1992; 1997; Dahlgren & Trillingsgaard, 1996).

Higher functioning individuals with ASD are usually only impaired in tests of intuitive mental state understanding (e.g., irony in language, see Happé, 1994a; Bowler, 2007), despite showing diminished episodic memory (Bowler et al., 2000a, b, 2007; Tanweer et al., 2010, replicated in the current thesis Experiments 2 and 4). Moreover, higher functioning individuals who pass higher order ToM tasks have nevertheless been shown to fail non-verbal preferential looking versions of false belief tasks (Senju, Southgate, White & Frith, 2009). Senju et al., (2009) using a task first developed by Onishi and Baillargeon (2005), tested understanding of false belief in adults with ASD using a non-verbal form of the ToM task. The authors demonstrated that individuals with ASD unlike matched individuals with TD, did not look substantially longer when an actor searched in a location for a hidden object that s/he could not know about. That is to say, TD individuals showed preferential looking towards an unexpected outcome (when the actor’s behaviour was inconsistent with their belief), whereas ASD individuals did not. The finding that individuals with ASD who pass higher order, verbal ToM tasks, can also fail non-verbal versions of the task suggests that language and thought are not as closely intertwined in ASD, as in TD. Furthermore, these results echo the findings of Williams et al., (in press) and are in line with the ERP findings reported in the current thesis.

8.5.4 The Weak Central Coherence Account

The last theoretical account to be discussed is WCC (Happé & Frith, 2006, see Chapter 1). WCC is the notion that individuals with ASD are more likely to process complex stimuli by focusing on the details rather than the overall configuration (highlighting the tendency for a detail- focused cognitive style for people with ASD, see Happé & Frith, 2006). This tendency for local- level processing has been noted in several other theories of ASD, including the theory of Enhanced Perceptual Functioning (Mottron et al., 2006) and Enhanced Discrimination (Plaisted, 2001), (see p. 18). By definition, episodic Remember responses involve combining various pieces of information together, for example, combining the spatial and temporal context of a previously experienced event into a multi-feature representation (Schacter & Tulving, 1994). In this way, episodic memory could be argued to require a global (rather than local) processing style. It is possible to speculate that tests of episodic memory and tasks involving a global processing style, both tap a similar mechanism, however, there is currently no robust evidence that links episodic/semantic memory and WCC. Future research could assess the relationship

between WCC and diminished episodic memory in ASD by testing a large sample of individuals with ASD (and a matched TD group) on a series of tasks aimed at assessing each of these cognitive functions. Episodic memory could be assessed with multiple measures such as the Remember/Know paradigm (Tulving, 1985b), Source monitoring tasks (Wheeler et al., 1997), free recall tasks (Perner & Ruffman, 1995) and tests of ‘episodic future thinking’ or ‘prospection’ (see Suddendorf & Corballis, 1997; Wheeler et al., 1997; Buckner & Carroll, 2007; Lind & Bowler, 2010). Multiple measures of WCC would also be gathered, for example, the Block Design test, Embedded Figures Test and tests of homograph reading (see section 1.2.1 of this thesis, also see Happé & Frith, 2006). With these data, it would be possible to run a regression analysis to uncover the extent to which these two phenomena overlap. However, because there is no current evidence to link WCC and episodic memory, the findings presented in this thesis will not be interpreted any further according to this account.