Contextual Modulation: Components of the Rod-and-Frame Illusion and the Systemizing Trait of Autism
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Date
2016-06
Authors
Adams, David John
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
Individuals with autism tend to have superior sensory discrimination abilities
and a locally-oriented cognitive style. The mechanisms that underlie these phenomena
are unknown and may be linked to atypicalities in the contextual modulation occurring
through mutually inhibitory interactions of neurons in early visual cortex. Prior wo·rk, in
both monkeys and humans, has demonstrated that the perceived orientation of a line is
distorted when presented in the context of other tilted lines (flankers), with the
magnitude and direction of these effects dependent on the orientation and location of
the flankers. With collateral flankers, the test line is perceived to be tilted away from
flankers with 15 degree tilts, but this "perceptual repulsion" becomes smaller (or even a
"perceptual attraction") with smaller flanker tilts. Experiment I examined the
relationship between these contextual effects and the systemizing trait of autism.
Individuals who scored high on the "insistence on sameness" subcomponent of
systemizing were more sensitive in their orientation judgments, while showing a greater
repulsive effect of the flankers. However, when the flankers were replaced with a small
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tilted frame, the resulting repulsive effects (known as the Rod-and-Frame illusion) were
even larger, but they were uncorrelated with insistence on sameness.
In Experiment 2, we dissected the frame into its component parts in an attempt
to determine the specific features that drive the orientation contrast effects of the Rodand-
Frame illusion. We discovered that the left and right sides of the frame induced a
significantly smaller repulsive effect than lateral flankers of the same tilt. However, the
top and bottom of the frame induced a large repulsive effect that even exceeded that of
the intact frame. These results indicate that the Rod-and-Frame illusion is the result of
an underadditive combination of two independent contextual effects, though neither of
these effects are correlated with insistence on sameness. Future work should further
investigate this underadditivity, as well as the link between autism and local contrast
effects. Such work may provide clues into how neural architecture differs in individuals
with autism.
Description
85 pages. A thesis presented to the Department of Psychology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2016.
Keywords
Autism, Obsessive-Compulsive Disorder, Systemizing, Visual Perception, Illusion Susceptibility, Orientation Descrimination