Isolating the effect of one-dimensional motion signals on the perceived direction of moving two-dimensional objects

A considerable body of evidence suggests the existence of a two-stage mechanism for the detection of global motion. In the first stage the motion of elongated contours is extracted and then at the second stage these one-dimensional (1D) motion signals are combined. What is the nature of the computation carried out in combining the 1D motion signals towards forming a global motion percept? We devised a set of stimuli that differentiate between different possible computations. In particular, they distinguish between a velocity-space construction (such as intersection of constraints) and a linear computation such as vector averaging. In addition, these stimuli do not contain two-dimensional (2D) motion signals such as line intersections, that allow unambiguous determination of global velocity. Stimuli were presented in uncrossed disparity relative to the aperture through which they were presented, to reduce the effect of line terminator motion. We found that subjects are unable to detect the veridical global direction of motion for these stimuli. Instead, they perceive the stimulus pattern to be moving in a direction which reflects the average of its 1D motion components. Our results suggest that the visual system is not equipped with a mechanism implementing a velocity-space computation of global motion.

[1]  P. Thompson.  Perceived rate of movement depends on contrast , 1982, Vision Research.

[2]  James T. Todd,et al.  The perception of globally coherent motion , 1992, Vision Research.

[3]  Ellen C. Hildreth,et al.  Measurement of Visual Motion , 1984 .

[4]  Hugh R. Wilson,et al.  Perceived direction of moving two-dimensional patterns depends on duration, contrast and eccentricity , 1992, Vision Research.

[5]  H. Wilson,et al.  A psychophysically motivated model for two-dimensional motion perception , 1992, Visual Neuroscience.

[6]  G. Orban,et al.  Response to movement of neurons in areas 17 and 18 of the cat: direction selectivity. , 1981, Journal of neurophysiology.

[7]  Maggie Shiffrar,et al.  The influence of terminators on motion integration across space , 1992, Vision Research.

[8]  G. Orban,et al.  Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity. , 1981, Journal of neurophysiology.

[9]  David R. Badcock,et al.  Two-stage analysis of the motion of 2-dimensional patterns, what is the first stage? , 1992, Vision Research.

[10]  K. Nakayama,et al.  Occlusion and the solution to the aperture problem for motion , 1989, Vision Research.

[11]  Claude L. Fennema,et al.  Velocity determination in scenes containing several moving objects , 1979 .

[12]  K. Nakayama,et al.  The aperture problem—I. Perception of nonrigidity and motion direction in translating sinusoidal lines , 1988, Vision Research.

[13]  E. Adelson,et al.  The analysis of moving visual patterns , 1985 .

[14]  Manuel Suero,et al.  Motion of complex patterns is computed from the perceived motions of their components , 1991, Vision Research.

[15]  K. Nakayama,et al.  The aperture problem—II. Spatial integration of velocity information along contours , 1988, Vision Research.

[16]  Vincent P. Ferrera,et al.  Perceived speed of moving two-dimensional patterns , 1991, Vision Research.

[17]  Ellen C. Hildreth,et al.  Computations Underlying the Measurement of Visual Motion , 1984, Artif. Intell..

[18]  E. Adelson,et al.  Phenomenal coherence of moving visual patterns , 1982, Nature.

[19]  Hans Wallach.  Über visuell wahrgenommene Bewegungsrichtung , 1935 .

[20]  H. Wilson,et al.  Perceived direction of moving two-dimensional patterns , 1990, Vision Research.

[21]  Leslie Welch,et al.  The perception of moving plaids reveals two motion-processing stages , 1989, Nature.

[22]  G. Orban,et al.  Factors influencing velocity coding in the human visual system , 1984, Vision Research.

[23]  S. McKee,et al.  Precise velocity discrimination despite random variations in temporal frequency and contrast , 1986, Vision Research.