A review of: Emma J. Grinter, Pia L. Beek, Murray T. Maybery, David R. Badcock (2008). Brief Report: Visuospatial Analysis and Self-Rated Autistic-Like Traits Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-008-0658-3

Although most psychiatric, developmental, and neurological disorders are usually conceptualized as discrete categories (e.g., you either have autism or you don’t), these conditions can also be conceptualized as occurring in a continuum. For example, we all feel sad sometimes. Such sadness, and related symptoms, can range from very mild to incapacitating. Somewhere in this continuum there is a theoretical line that separates sadness from clinical depression.

In autism, a number of researchers have proposed the concept of the Broader Autism Phenotype. This concept refers to mild traits of autism found in the general typically developing population, and especially among relatives of people with Autism. You can read a couple of summaries of research on the Broader Autism Phenotype here and here.

In this study, the authors were interested in examining whether typically developing young adults (college students) who have high levels autism-like traits also have relative strengths on tasks of visospatial skills – a finding that is common among people with some autism spectrum disorders. The authors presented two studies. In the first study they examined 548 college students in Australia. The students completed the Autism-spectrum Quotient (AQ), which is a measure of autistic traits. A subsample of these students then completed two visuospatial tasks: the block design of the Wechsler Adult Intelligence Scales and the Embedded Figures Test. The authors reported that students with high AQ scores outperformed those with low AQ scores in both the block design task and the Embedded Figures Test. In a second study, the authors examined the effects of general IQ on these results. They showed that IQ partially explained the group differences in the Embedded Figures Test, but IQ did not explain the differences in the block design task. That is, these two groups continued to show differences in performance on the block design task even when considering differences in IQ between the groups.

The authors explained their results in the context of the Weak Central Coherence Theory. This theory suggests that some individuals (e.g., people with autism) have a “lack of distraction by holistic configurations and relative facilitation in dealing with piecemeal components.” This in turn would facilitate visuospatial tasks that require significant attention to detail.

There is one methodological issue I wish you briefly note. The authors initially examined 548 students. Then only those who scores significantly low and high in the AQ scales were invited to complete the visuospatial tasks. These groups included only 20 students in the low AQ group and 19 students in the high AQ group. This represents the extreme 4% of the sample. I wish that the entire sample of 548 students had completed all tasks and that the data were presented without categorizing the sample as low and high AQ. Instead the data could have been presented in a continuum to show whether high scores in the AQ were also associated (correlated) with high scores on the block design task and the Embedded Figures Test. This would provide a much stronger argument for the fluidity of autism-like traits in the general population and its association with other cognitive skills observed in autism.

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4 Responses to The Continuum of Autism: Visuospatial skills and Autistic Traits.

  1. Socrates says:

    I wrote about an astonishing new study from the ARC in Cambridge, showing a substantial difference in the visual acuity in people with an ASC. It would be interesting to see if a difference is also found in people in the BAP range.

    I can’t understand why this study hasn’t been all over the media – it was one of the most remarkable research papers I’ve read for ages.

    http://the-newrepublic.blogspot.com

  2. RAJ says:

    The presence of what has been called the BAP is certainly present in the extended pedigrees of children diagnosed with an ASD. There is a general consensus that the ’cause’ of autism is a disruption of early brain development but the etiolgy remains unknown.

    Several groups have recruited large samples of twins from twin registries in the Netherlands, the UK an the US and administered various questionnaires scoring what has been variously described as the BAP, subthreshold autistic-like traits and autistic-like traits all of which represent the genetic liability to autism in the general population. Happe, Arnold and Plomin have published cuttof points for the liability to autism in the general public, describing 5% of the general population as possessing ‘extreme autistic-like traits’ and 10% of the entire large sample possessing at least one autistic-like trait.

    The finding that the genetic liability to autism in the general public of between 5% and 10% with a mean of 7.5% which is more than 10 times greater than the prevelance of ASD’s in the general population as published by the CDC in the US (.667) does not suggest the presence of a genetically transmitted condition.

    What is known about the parents is that they do not posses the structural abnormalities that have been consistently reported in ASD’s.

    All of this suggests a gene-environmental interaction etiolgy for the bulk of the cases ie. the interaction of the genetic liability to autism in the general population and unfavorable events in the pre, peri and neonatal period that are known to disrupt early brain development (see Rubella autism, Valproate Acid Syndrome, Thalidomide embryopathy etc).

  3. Socrates says:

    Dear old RAJ,

    What would we do without you?…

    Have a look at studies of the neurological imaging of BAPpies… They show exactly the same kind of “abnormal”, “pathological” patterns of functioning as autistics.

    Hint: ARC Cambridge

  4. RAJ says:

    “Have a look at studies of the neurological imaging of BAPpies… They show exactly the same kind of “abnormal”, “pathological” patterns of functioning as autistics”

    ARC uses functional imaging is useful to examine brain function of people diagnosed with an ASD and their unafected parents. The functional diferences are not necessarily abnormal or pathological, but represent brain function common to family traits.

    The structural abnormalities seen in autism are microscopic and can only be observed at autopsy. Several decades of in depth microscopic neuropathological studies have consistently found structual abnormalities in various brain regions, primarily a massive loss of cerebellar Purkinge cells and a disruption in limbic system regions (there are too many cells and they are too small). Other structural defects have been found in frontal lobes and occasionally other brain regions.

    The findings from functional MRI studies suggests that certain traits are shared by ASD patients and their first degree relatives but microscopic autopsy results show microscopic structural abnormalities not found in fist degree relatives… They do not demonstrate the isolated neuorlogical symptoms that are part of the various diagnostic tools used to make an ASD diagnosis.

    That is where the concept of autistics traits being on a continuum from profoundly handicapped to normal falls apart. The cutoff point that seperates an ASD from autistic-like traits (which are not autism per se) is the disruption of early brain development found in ASD but not in BAP

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