Cyclopean flash-lag illusion.
Possible physiological mechanisms to explain the flash-lag effect, in which subjects perceive a flashed item that is co-localized with a moving item as trailing behind the moving item, have been found within the retina of lower species, and in the motor pathways of humans. Here, we demonstrate flash-lag employing "second-order" moving and flashed stimuli, defined solely by their binocular-disparity, to circumvent any possible "early" contributions to the effect. A significant flash-lag effect was measured with cyclopean stimuli composed entirely of correlated random dot patterns. When the disparity-defined moving stimulus was replaced with a luminance-defined one, potentially engaging retinal mechanisms, the magnitude of the measured effect showed no significant change. Thus, in primates, though retinal mechanisms may contribute, flash-lag must be explained through cortical processes.
Nieman
Dylan
D
Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. nieman@caltech.edu
Nijhawan
Romi
R
Khurana
Beena
B
Shimojo
Shinsuke
S
D000221:Adaptation, Ocular; D002540:Cerebral Cortex / Q000502:physiology; D006801:Humans; D007600:Judgment; D008027:Light; D009039:Motion Perception / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011594:Psychometrics; D012160:Retina / Q000502:physiology; D015357:Vision Disparity / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology