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Induced motion of a fixated target: influence of voluntary eye deviation
T Heckmann1, R B Post, L Deering
1General Motors Research Laboratories, Warren, MI 48090-9055.
Perception & Psychophysics
|September 1, 1991
Summary
Induced motion (IM) causes a fixated target to appear to move opposite to background motion. This illusory motion is linked to the effort needed to suppress involuntary eye movements, supporting the nystagmus-suppression hypothesis.
Area of Science:
- Neuroscience
- Visual Perception
- Ophthalmology
Background:
- Induced motion (IM) is a visual illusion where a stationary object appears to move due to the motion of surrounding objects.
- Previous explanations for IM include visual capture, afferent mechanisms, and egocenter deviations.
Purpose of the Study:
- To investigate the relationship between fixation eccentricity and the magnitude of induced motion.
- To test the nystagmus-suppression hypothesis as an explanation for induced motion.
Main Methods:
- Participants fixated on a target while a background moved.
- Fixation position was varied (straight ahead, 10 degrees same direction, 10 degrees opposite direction of background motion).
- Magnitude of induced motion in the fixated target was measured.
Main Results:
- Induced motion was observed in the direction opposite to background motion.
- IM decreased when fixation was deviated in the same direction as background motion.
- IM increased when fixation was deviated in the opposite direction of background motion.
Conclusions:
- The results support the nystagmus-suppression hypothesis, suggesting illusory motion magnitude correlates with voluntary efference to oppose involuntary eye movements.
- This hypothesis explains various forms of subjective motion, including autokinesis and the oculogyral illusion.
- Other proposed mechanisms do not fully account for the observed findings.