A moving-barber-pole illusion.
In the barber-pole illusion (BPI), a diagonally moving grating is perceived as moving vertically because of the shape of the vertically oriented window through which it is viewed-a strong shape-motion interaction. We introduce a novel stimulus-the moving barber pole-in which a diagonal, drifting sinusoidal carrier is windowed by a raised, vertical, drifting sinusoidal modulator that moves independently of the carrier. In foveal vision, the moving-barber-pole stimulus can be perceived as several active barber poles drifting horizontally but also as other complex dynamic patterns. In peripheral vision, pure vertical motion (the moving-barber-pole illusion [MBPI]) is perceived for a wide range of conditions. In foveal vision, the MBPI is observed, but only when the higher-order modulator motion is masked. Theories to explain the BPI make indiscriminable predictions in a standard barber-pole display. But, in moving-barber-pole stimuli, the motion directions of features (e.g., end stops) of the first-order carrier and of the higher-order modulator are all different from the MBPI. High temporal frequency stimuli viewed peripherally greatly reduce the effectiveness of higher-order motion mechanisms and, ideally, isolate a single mechanism responsible for the MBPI. A three-stage motion-path integration mechanism that (a) computes local motion energies, (b) integrates them for a limited time period along various spatial paths, and (c) selects the path with the greatest motion energy, quantitatively accounts for these high-frequency data. The MBPI model also accounts for the perceived motion-direction in peripherally viewed moving-barber-pole stimuli that do and do not exhibit the MBPI over the entire range of modulator (0-10 Hz) and carrier (2.5-10 Hz) temporal frequencies tested.
Department of Cognitive Sciences, University of California Irvine, Irvine, CA, USA.
Peng
P
Sun
Charles
C
Chubb
George
G
Sperling
D000328:Adult; D003198:Computer Simulation; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008027:Light; D009039:Motion Perception / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D055815:Young Adult
2D motion; Barber-Pole-Illusion; form-motion-interaction; motion integration; motion model