This study focused on specific conceptual, methodological and developmental issues pertinent to investigating the role of attention in global-local processing among high-functioning children with autism (average verbal mental age (MA) of 89 months and nonverbal MA of 116 months) as compared to their verbal and nonverbal MA matched peers. Two experiments were conducted to assess separately basic processing; focal attention that is drawn by the physical properties of the stimuli and higher-order processing associated with strategically directing attention in accordance with the observer's priorities within a given task. These components of attention are implicated in the typical development of global-local perceptual organization. / In Experiment 1, a visual search task was used to explore the role of basic focal attention to perceptually group dots at either a long or short spatial range. In Experiment 2, a visual search and target identification task was used to assess higher-order voluntary control of attention to the global or the local level of a hierarchical geometric pattern. To assess changes in voluntary attending to a specific target level, an implicit manipulation of increased probability of the target appearing at the global or local level or equally at both levels was included. / The main finding was that high-functioning children with autism and their verbal and nonverbal MA matched peers showed comparable focused attention to perceptually organize stimuli over a short or long spatial range but different higher-order attentional processing of hierarchical global-local targets. In all groups, search efficiency for long range targets decreased as a function of display size but the search for short range targets was efficient regardless of display size. Long range grouping performance involves goal-driven, focused attention that is constrained by serial inspection whereas the short range grouping performance implicates a sensory-driven, preattentive spatial-indexing mechanism. At higher levels of attentional control, high-functioning children with autism show a preference for using a local attentional strategy whereas their typically developing peers rely on a global attentional strategy to search for hierarchical global-local targets among distractors. The particular style of visual processing used to search for targets was not influenced by implicit changes in the probability of a target appearing at the local or global level. The findings support the interpretation that a perceptual disturbance in global-local processing in persons with autism may be associated with different higher-order strategy-based processing rather than an enhanced ability to integrate features.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36955 |
| Date | January 2000 |
| Creators | Iarocci, Grace. |
| Contributors | Burack, Jacob A. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Educational and Counselling Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001810840, proquestno: NQ70046, Theses scanned by UMI/ProQuest. |
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