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Now you see it, now you don't : a case study of perceptual alternations

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Mapperson, Barry Norman (1989) Now you see it, now you don't : a case study of perceptual alternations. PhD thesis, University of Tasmania.

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Abstract

Under some conditions, what we are seeing or hearing can seem to
change abruptly, radically, and apparently spontaneously even though
the physical stimulus does not alter. Although these 'perceptual
alternations' occur with a bewilderingly varied range of stimuli, the
evidence suggests that they are all the result of a common central
process, which periodically switches between different interpretations
of the stimulus.
The 'square-wave illusion' is one form of perceptual instability which
has been claimed to be an exception to this rule,'with,not one but two
completing explanations in terms of peripheral Mechanisms having
been advanced. The explanation at the most peripheral level that in
terms of established cortical mechanisms is not, it is argued, compatible
with a more detailed analysis of the literature. Explanations in terms of
central processes, however, are supported by experiments in which cues
such as edge information, the actual or implicit position of a light
source, and instructional set are manipulated.
In addition the relative dominance of the percepts can be altered in
opposite directions by the prior inspection of stimuli which are
physically similar (but phenomenally dissimilar) implicates central
processes in this effect. Nevertheless, it is argued that a full explanation
of the effect must take into account the manner in which the
peripheral mechanisms process the visual information. Support for this comes from the finding that movement relative to the retina (i.e. either movement of the stimulus with steady fixation or making eye movements across a stationary stimulus systematically distorts the perception of the illusion. Two possible explanations of this distortion are evaluated.
On the basis of the experiments and analyses presented in this thesis, it is argued that the square-wave illusion should not be regarded as a 'special case', but rather as merely one further manifestation of a more general mental process.

Item Type: Thesis (PhD)
Keywords: Visual perception, Optical illusions
Copyright Holders: The Author
Copyright Information:

Copyright 1989 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1990. Bibliography: leaves 74-84

Date Deposited: 19 Dec 2014 02:32
Last Modified: 15 Sep 2017 01:03
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