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Article
Orientation illusions induced by briefly flashed plaids
Perception
  • Peter Wenderoth, Macquarie University
  • Rick van der Zwan, Southern Cross University
  • Syren Johnstone
Document Type
Article
Publication Date
1-1-1989
Peer Reviewed
Peer-Reviewed
Abstract
Orientation illusions which occur when a vertical grating is surrounded by a plaid can be induced either by one of the plaid's orthogonal component gratings or by a virtual axis of symmetry of the plaid, whichever is nearest vertical. In six experiments in which such illusion displays were flashed for durations between 15 and 405 ms, it was found that when these two-dimensional illusions are induced by a component grating (direct effects) the illusions increase monotonically as duration decreases, from l° - 2° to about 6° - 7°, over this range. Effects induced by axes of symmetry (indirect effects), in contrast, begin to occur only at longer durations: for short exposures, illusions are directionally opposite and large, similar to direct effects. These results suggest that only plaid-component-selective mechanisms operate at the shortest exposure durations and that additional time is required to extract more global higher-order pattern structure. The data are discussed in relation to sustained and transient mechanisms and also with respect to recent reports of more global processing mechanisms in extrastriate cortex and related data on one-dimensional tilt illusions.
Disciplines
Citation Information

Wenderoth, P, van der Zwan, R & Johnstone, S 1989, 'Orientation illusions induced by briefly flashed plaids', Perception, vol. 18, no. 6, pp. 715-728.

Published version available from:

http://dx.doi.org/10.1068/p180715