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Perceptual Processing in Autism

Perceptual Processing in Autism. Weak Central Coherence. Autism. Triad of Impairments (Wing and Gould, 1979) Socialisation, communication, and imagination.

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Perceptual Processing in Autism

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  1. Perceptual Processing in Autism Weak Central Coherence

  2. Autism • Triad of Impairments (Wing and Gould, 1979) Socialisation, communication, and imagination. • Non-social features -restricted area of interest/ preoccupation with parts of objects -desire for sameness and routine -excellent rote memory -savant abilities -islets of ability

  3. Weak Central Coherence (WCC) • Frith (1989) proposed that all features of autism could be explained by a single deficit in processing information • WCC involves two parts: Perceptual- a preference to process information locally rather than globally Conceptual-a failure to process contextual meaning or use prior knowledge

  4. Individuals with autism were significantly faster than matched controls Block Design Test (Shah & Frith, 1993)

  5. Individuals with autism were significantly faster at locating the hidden figure than matched controls. Embedded Figures Test (Shah & Frith, 1983)

  6. Autistic savant artists

  7. Snowling and Frith (1986) • Those with autism fail to use context when processing ambiguous homographs. e.g. The actor took a bow. * Failure to process context = poor performance in autism

  8. -hat -cow -peach -doll -boat -pencil -apple -car -banana -pear -mug -cherry Tager-Flusberg (1991)

  9. First attempt to explore low-level visual integration in autism Found individuals with autism were less susceptible to illusions than matched controls Happe (1996)

  10. Limitations of Happe’s study • Methodological -Verbal responses may be susceptible to bias –Does not tell us degree of susceptibility • Theoretical -No independent measure of WCC included to confirm perception of illusions requires same underlying ability as other CC tasks.

  11. Research questions • Can Happe’s findings be replicated using a more precise and better controlled measure of susceptibility? • Do measures of WCC predict susceptibility to illusions?

  12. Four size illusions and their controls were presented on a laptop computer. Subjects were instructed to use buttons on the keyboard to adjust parts of the illusion until they looked the same. Ropar and Mitchell (2001)

  13. Visual spatial tasks used as measures of WCC

  14. Subject Characteristics

  15. Titchener illusion

  16. Muller-Lyer illusion

  17. Ponzo illusion

  18. Hat illusion

  19. Block Design Test

  20. Embedded Figures Test

  21. Rey Test

  22. Correlations between illusions

  23. Correlations between visuo-spatial tasks*indicates significance with a Bonferroni correction of.005

  24. Correlations between visuo-spatial tasks and illusions Note: consistent with prediction / opposite to prediction

  25. Summary of findings • Can Happe’s findings be replicated using a more precise and better controlled measure of susceptibility? No • Do measures of WCC predict susceptibility to illusions? Not in a way that supports Happe. • Individuals with autism performed well in comparison to control groups on visuo-spatial tasks.

  26. Do individuals with autism perform well due to less capture by ”wholeness” or “meaning”?

  27. Brian and Bryson (1996)

  28. Superiority in visual search O’Riordan et al (2001)

  29. Narrowing of attentional spreadMann & Walker (2003)

  30. ssssssssss ssssssssss s s s s s s s Could explain Navon data

  31. Boundary ExtensionIntraub (1990)

  32. Chapman, Ropar, Mitchell & Ackroyd (2004)

  33. Results • Clear boundary extension, with a mean value of 12.51% (i.e. as if 12.5% further away): , t(35) = 10.78, p < .001, d = 1.80. • The degree of boundary extension was virtually identical between those with and without autism

  34. Summary • Contrary to prediction, boys with Asperger syndrome show at least as much boundary extension as comparison participants • Narrowing of attentional spread? • Sensitivity to the wider context?

  35. Ellipse not slanted Perspective slanted Knowledge slanted Ropar and Mitchell (2002) Viewing Condition Stimulus Shape Projected Shape

  36. Subject Characteristics

  37. Judgments of shape in each condition.

  38. Summary of findings • Individuals with autism are less affected by prior knowledge, but are equally affected by perspective cues.

  39. Theoretical implications • Atypical visual processing in autism is better understood in terms of difficulties with integrating conceptual information.

  40. Evidence showing those with autism do utilise meaning • Ropar and Mitchell, 2001 • Pring and Hermelin, 1993 • Ameli et al., 1988

  41. 3 levels of coherence (Happe 1999) • Perceptual -Little evidence • Visuo-spatial constructional - Fairly strong evidence (but are these conceptual?) • Verbal semantic (conceptual) -Mixed evidence

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