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Second-order reversed phi.
1Department of Psychology, University of Southern California, Los Angeles 90089, USA. zhonglin@ref.usc.edu
Perception & Psychophysics
|September 25, 1999
Summary
This study reveals that perceived motion direction depends on visual system pathways. Second-order motion perception, particularly reversed-phi stimuli, involves competing mechanisms influencing direction depending on viewing conditions.
Area of Science:
- Visual perception
- Motion detection
- Psychophysics
Background:
- First-order reversed-phi motion stimuli involve contrast reversal, potentially leading to apparent motion reversal.
- Perceiving forward motion with these stimuli engages higher-order visual motion systems.
Purpose of the Study:
- To investigate novel second-order reversed-phi stimuli invisible to first-order motion analysis.
- To determine the roles of second- and third-order motion systems in perceived motion direction.
Main Methods:
- Construction of three novel second-order reversed-phi stimuli (contrast, spatial frequency, flicker modulation).
- Testing perception of these stimuli in peripheral and central vision across various temporal frequencies.
- Analyzing observer responses based on motion energy models and feature displacement.
Main Results:
- Second-order reversed-phi stimuli activate competing motion mechanisms.
- Peripheral vision and central vision at high temporal frequencies predominantly perceive reversed motion.
- Central vision at low temporal frequencies (<4 Hz) perceives forward motion.
Conclusions:
- The second-order motion system (Reichardt detector/motion energy) predicts reversed motion.
- The third-order motion system (salience map) predicts forward motion.
- The dominance of perceived motion direction depends on the system's spatial-temporal resolution and viewing conditions.