Perceptual Processing in Autism Weak Central Coherence

Autism Triad of Impairments (Wing and Gould, 1979) Socialisation, communication, and imagination. 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 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

Weak Central Coherence (WCC) Frith (1989) proposed that all features of autism could be explained by a single deficit in processing information 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 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

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

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

Autistic savant artists

Snowling and Frith (1986) Those with autism fail to use context when processing ambiguous homographs. 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

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

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

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

Research questions Can Happes findings be replicated using a more precise and better controlled measure of susceptibility? Can Happes findings be replicated using a more precise and better controlled measure of susceptibility? Do measures of WCC predict susceptibility to illusions? Do measures of WCC predict susceptibility to illusions?

Ropar and Mitchell (2001) 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.

Visual spatial tasks used as measures of WCC

Subject Characteristics GroupMLDAutistic Year 3 Year 6 Asperger n CAmeanrange12;119;2-14;814;29;3-18;38;67;7-8;611;310;9-11;711;108;4-15;4 VMAmeanrange6;113;3-10;106;113;8-13;48;05;3-10;611;69;5-15;79;115;1-17;6

Titchener illusion

Muller-Lyer illusion

Ponzo illusion

Hat illusion

Block Design Test

Embedded Figures Test

Rey Test

Correlations between illusions HatPonzo Muller- Lyer Titchener XXX r=.23, p<.05 r=-.25, p<.05 r=.01, p=.935 Hat XXX r=-.13, p=.262 r=-.11, p=.352 Ponzo XXX r=.03, p=.774 Muller- Lyer XXXTitchener

Correlations between visuo-spatial tasks *indicates significance with a Bonferroni correction of.005 EFT EFT BDT BDT Rey copy Rey recall XXX *r=-.81, p<.001 *r=-.68, p<.001 *r=-.49, p=.001 EFT XXX *r=.72, p=.001 *r=.57, p=.001 BDT XXX *r=.71, p=.001 Rey copy XXX Rey recall

Correlations between visuo-spatial tasks and illusions Group Group EFT EFTBDT Rey copy Rey recall Autistic - -Hat(.66) - Asperger MLD Muller (.55) Muller (-.50) - - Year Year 6 Muller (.74) Muller (-.73) Muller (-.54) Muller (-.62) Note: consistent with prediction / opposite to prediction

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

Do individuals with autism perform well due to less capture by wholeness or meaning?

Brian and Bryson (1996)

Superiority in visual search ORiordan et al (2001)

Narrowing of attentional spread Mann & Walker (2003)

Could explain Navon data ssssssssssssssssssss ssssssssssssssssssss s s s s s s s

Boundary Extension Intraub (1990)

Boys with Asperger syndrome Matched control boys N18 Age (y;m)Mean14;013;6 SD2;01;7 Range9;7-16;510;11-15;8 Verbal IQMean SD Range Performance IQMean SD Range Full scale IQMean SD Range Chapman, Ropar, Mitchell & Ackroyd (2004)

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 = 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 = The degree of boundary extension was virtually identical between those with and without autism The degree of boundary extension was virtually identical between those with and without autism

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

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

Subject Characteristics GroupAutisticMLD Age 9 Adults n CA CA mean mean range range13;6(9;7-18;11)13;6(11;0-15;6)9;4(8;10-9;9)26;5(15;10-48;7) VMA mean mean range range8;0(2;9-15;7)8;5(5;11-12;5)9;4(8;10-9;9)-

Judgments of shape in each condition.

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

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

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

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