Autism-a two dimensional disorder?
Two main underlying deficits have been proposed in autism– one concerning an inactive or non-existent Theory of Mind module and another a tendency towards Weak Central Coherence. ToM defects reflect in the communicative, social and imaginative deficits seen in autistics; while the savant skills as well as restrictive and repetitive behavior (restricted repertoire of interests ;obsessive desire for sameness – islets of ability – idiot savant abilities – excellent rote memory – preoccupation with parts of objects ) are best explained by taking recourse to the Autism-as-a cognitive-style having weak Central Coherence argument. I’ve discussed the crucial aspects of both of these two dimensions in y series of posts on autism and psychosis and shown how they have to be seen on a continuum and more as deviation from the normal range with one end as autism and the other as psychosis. We also know that psychosis itself is two dimensional with one dimension being that of schizophrenic spectrum and the other the bipolar spectrum. Thus what I propose is that we start seeing Autism also as a two dimensional disorder with TOM defect subtype a mirror image of schizophrenia; while the Weak CC subtype a mirror image of bipolar or manic depressive phenotype. Here are autistic and psychotic features on these dimensions (from Autism, Happe, the autistic deficits and assets table):
- ordering behavioural pictures (Baron-Cohen et al. 1986) vs ordering mentalistic pictures understanding “see” (Perner et al. 1989)
- understanding “know” protoimperative pointing (Baron-Cohen 1989c) vs protodeclarative pointing sabotage (Sodian & Frith 1992)
- deception false photographs (Leekam & Perner 1991, Leslie & Thaiss 1992) vs. false beliefs recognising happiness and sadness (Baron-Cohen et al. 1993a)
- recognizing surprise object occlusion (Baron-Cohen 1992) vs. information occlusion
- literal expression (Happé 1993) vs. metaphorical expression
- elicited structured play (Wetherby & Prutting 1984)vs. spontaneous pretend play
- instrumental gestures (Attwood et al. 1988) vs. expressive gestures
- talking about desires and emotions (Tager-Flusberg 1993) vs. talking about beliefs and ideas
- using person as tool (Phillips 1993) vs. using person as receiver of information
- showing “active” sociability (Frith et al. 1994) vs. showing “interactive” sociability
It is also pertinent in this regard to revisit the question of co-occurrence of autism and schizophrenia. Happe maintains that psychois can only be relaibly seen in Asperge’s group who might have a late developing ToMm ability. To quote:
The higher incidence of psychiatric disorders in this group (asperger’s group) (Tantam 1991, Szatmari et al. 1989b) is well explained by this hypothesis. Depression will be more common since these people have greater insight into their own difficulties and their own feelings and thoughts. Positive symptoms of psychosis, such as hallucinations and delusions would be found only in Asperger’s syndrome cases by this account, if one takes Frith & Frith’s (1991) view of these symptoms as resulting from an “over-active” theory of mind. Asperger’s syndrome people, who gain theory of mind late and therefore abnormally, may be at high risk for having their theory of mind “go wrong”. On this hypothesis it would be impossible for a Kanner-type autistic person (who has no theory of mind) to show these psychotic or positive symptoms. In this sense (according to Frith & Frith’s theory) Asperger’s syndrome would be something of a midpoint between autism and (positive or florid) schizophrenia; while the former is due to a lack of theory of mind, and the latter due to over-active theory of mind, some people with Asperger’s syndrome may show both the scars of early lack and the florid symptoms of late acquired theory of mind working abnormally hard.
There is some preliminary evidence to support the suggestion that the term “Asperger’s syndrome” could meaningfully be restricted to those subjects with autism who have achieved some ability to think about thoughts. Ozonoff et al. (1991) found that their group labelled (perhaps arguably) as having Asperger’s syndrome did not show impairments relative to controls.
It is interesting to note the ‘over-active’ theory of mind reference to Frith and Frith. I could not locate that paper but came across another paper by Abu-akkel that propose over-active ToM as a mechanism of psychosis. There are also some full text related articles available online that may be of interest to the serious reader. As for me, it is heartening to note that others concur with the theory of autism and psychosis as opposites on a continuum.
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