Experimental data to test the theory that individuals with autism rely less on top-down processing. The influence of knowledge on perception was explored on two different levels. Firstly, we examined the encoding or input of information in those with and without autism. A second level in which the influence of top-down processing was explored is related to the output of knowledge. Three studies were carried out to investigate whether higher-level knowledge interferes with the ability to perceive a stimulus accurately in those with autism as it does in those with typical development. Autism is a developmental disorder that afflicts at least 1 child per ten-thousand, and perhaps as many as 1 in one-thousand. There is currently an increasing rate of diagnosis for reasons unknown. There is no cure, and afflicted individuals are destined to live with the disorder indefinitely, though with suitable programmes of intervention, individuals can adapt somewhat. The disorder is diagnosed according to behavioural criteria and impairments are apparent in communication, socialisation and imagination. Many individuals with autism also have associated learning difficulties, though some are high functioning and may even have measured intelligence that is higher than the population average. Autism in these individuals might be referred to as Asperger syndrome. Despite the impairments in autism, another characteristic is relatively heightened visuo-spatial abilities. Frith explains this paradox by suggesting that individuals with autism have weak central coherence, meaning that they tend to process piece-meal rather than holistically. So, for example, individuals with autism have an aptitude for detecting a small shape embedded in a larger figure. Whereas individuals without autism are hampered by their apprehension of the overall figure, those with autism readily process the stimulus in its constituent parts. Relatedly, it seems individuals without autism bring their conceptual knowledge to bear on encoding and reproduction (e.g. as in their drawings) of a stimulus, while those with autism perhaps are not so influenced by conceptual knowledge and are thus equipped to reproduce the stimulus more faithfully. The purpose of the proposed research is to conduct 4 systematic investigations into the encoding and the output of information in individuals with autism to establish the following. (1) Are they more effective in encoding visual than verbal input, as commensurate with their generally heightened visuo-spatial abilities? (2) Are their depictions faithful because they are not hampered by conceptual knowledge? In the first investigation, individuals with autism will be presented with a list either in words or pictures, either in the presence or absence of a theme cue that links the items. We expect those with autism to be better at recalling pictures than words and indeed to recall more of the pictorial information than comparison participants. We expect their recall of pictures to be so good, that the theme cue contributes no further help to retrieval, unlike in comparison participants. In the second, third and fourth investigations, we expect depictions made by individuals without autism to by contaminated by conceptual knowledge. We expect them to import material in some cases, while in other cases, we expect them to distort the shapes of presented stimuli. In other words, we expect the depictions to approximate towards what participants know about the presented objects. We expect the effect to increase, as the presented stimuli become more easily recognisable and classifiable as particular objects (Experiment 3). In contrast, we expect individuals with autism generally to depict the stimuli more accurately and we expect the recognisability of the stimulus object not to have such a marked effect in distorting depiction. The findings will tell us at least two things. They will tell us about the benefits of visually-based information for individuals with autism. For example, perhaps individuals with autism will be better at encoding and retaining material presented in pictures rather than words. The findings will also tell us about the autistic aptitude for faithful depiction, and especially its cognitive basis. Armed with this new knowledge, it will be possible to design programmes of curricula, intervention and therapy that are more closely suited to autistic cognitive characteristics. The findings will inform the construction of virtual environments for individuals with autism, in a project currently funded by the Shirley Foundation. In summary, the project will generate novel findings that are publishable in front-line journals, and it will also serve strategically to inform the applied work in the Shirley project
- Recall of words and pictures. In a study on word and picture recall, participants were presented with lists of related (e.g. animals) and unrelated items. Individuals with autism, Asperger’s Syndrome, and comparison groups were presented with two lists (one picture and one word list) and asked to recall as many items as possible. We predicted that unlike comparison participants, individuals with autism and Asperger’s Syndrome would fail to use the meaningful thematic link (e.g. animals) to facilitate recall of the related items. Furthermore, we predicted those with autism/Asperger’s Syndrome would show an exceptional advantage for recalling information presented in pictorial form. We were surprised to find that those with autism/Asperger’s Syndrome recalled more related than unrelated items, just as comparison participants without autism. There was also no evidence that those with autism/Asperger’s Syndrome had any unique advantage in recalling information presented as pictures. 2. Computer version of Sheppard task. The influence of conceptual knowledge on perception was explored by presenting individuals with the Sheppard illusion. The stimuli include two figures presented side by side which look like tables. Due to one’s knowledge about object properties, the table tops appear to be different sizes even though they are identical. The same shapes appear to be more identical when the table legs and features are removed and they simply appeared as parallelograms. The stimuli both with and without table features are presented to individuals on a laptop computer. A computer programme was designed to allow participants to adjust one shape to appear the same size as the other. We predicted that individuals with autism/Asperger’s Syndrome would be more accurate than comparison groups in estimating shape with the table stimuli. As predicted, we found that individuals with autism were better in judging shape of the table stimuli than comparison participants. Those without autism/Asperger’s Syndrome misjudged shape to a greater extent when the stimuli appeared as tables than when they appeared as parallelograms. A drawing version of the Sheppard task was presented to typically developing adults to see if the findings from the computer task could be replicated when individuals were required to copy the stimuli. Participants performed similarly to the comparison groups in the computer version of the task which shows that the effect is evident on computer and non-computer type tasks. 3. Boundary extension. Recall of photographs of scenes was explored in individuals with and without Asperger’s Syndrome. A computer programme was developed which presented 16 photos one at a time at a certain magnification. In a second phase the same photos were shown but each at a different magnification. Participants could adjust the magnification to increase or decrease the boundary of the scene by using the computer keys. They were asked to make the photos the same as how they appeared in the first presentation. We predicted that individuals without Asperger’s Syndrome would falsely recall seeing more of the boundary of a scene (i.e. show boundary extension), whereas those with Asperger’s Syndrome would be more accurate in recalling the correct magnification of the scene. Those with Asperger’s Syndrome did show boundary extension like typically developing adults, however they performed the task significantly faster. Further comparisons between those with Asperger’s Syndrome and age and ability matched participants is currently being completed. 4. Perception through a Da Vinci window. The influence of conceptual knowledge on perception of an object was explored using a Da Vinci window. A Da Vinci window is an apparatus which reduces the influence of depth cues on perception but not the influence of one’s knowledge about an object’s properties. The Da Vinci window consists of a wooden frame holding a transparent Plexiglas pane with a viewing hole in the centre. Individuals were asked to view an object through the window and select from among a number of shapes which one best matched the object. We expected individuals with Asperger’s Syndrome to find it easier to identify the correct shape on this task if they are less influenced by their prior knowledge. Contrary to expectations, there was no difference in performance between those with and without Asperger’s.
