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The Oxford Compendium of Visual Illusions$
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Arthur G. Shapiro and Dejan Todorovic

Print publication date: 2017

Print ISBN-13: 9780199794607

Published to Oxford Scholarship Online: June 2017

DOI: 10.1093/acprof:oso/9780199794607.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 28 September 2021

High Phi and Ghost Phi

High Phi and Ghost Phi

Extreme Motion Illusions

(p.592) Chapter 83 High Phi and Ghost Phi
The Oxford Compendium of Visual Illusions

Mark Wexler

Oxford University Press

When a moving stimulus is followed by certain transient events, an illusion of very fast motion is perceived, in which a random texture undergoes a slow rotation, but every second most observers perceive a very fast jump in the direction opposite to the preceding or “inducing” rotation. These jumps are illusory: during the perceived jump, every frame is a new, random texture, uncorrelated with the previous textures; the last of these random textures is set to turning once again, and the sequence repeats. Thus there is there is no specific correspondence between the textures before, during, and after the jumps and no motion energy corresponding to the jumps. These illusory jumps are called “high phi.” If the transient is immediately “undone,” a different kind of illusory motion is perceived, called “ghost phi.” This example shows a study of the effects of motion adaptation.

Keywords:   illusion, high phi, ghost phi, illusory jumps, motion, motion adaptation, transient

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