Perception of Motion in Equiluminous Kinematograms

Abstract

Two fields of random dots that were identical except for a slight shift in a central square region were presented in rapid alternation. This produced a vivid impression of a square moving back and forth above the background. When the kinematogram is presented in equiluminous red/green, the motion of the central region can still be seen, although over a narrower range of alternation rates, interstimulus intervals, and displacements than for black/white presentation. The perception of motion for equiluminous stimuli indicates that colour and motion can be analyzed conjointly by the visual system. However, as originally reported by Ramachandran and Gregory, the segregation of the oscillating central square from the background is lost at equiluminance. This segregation process therefore appears to be colour-blind.

Two carriers for motion perception: Color and luminance

“…This observation, together with similar ones, contained in a comprehensive study of a wide range of AM phenomena, led Cavanagh and Mather (1990) to argue in favor of a single AM process, rather than the two separate (short-range and long-range) AM processes proposed earlier (Braddick, 1974, Pantle & Picciano, 1976. Even if this dichotomy is valid, our stimuli are indeed difficult to classify as either shortor long-range for the following reasons: (1) The size of AX in our stimuli might classify them as long-range, although the relatively large size of the elements tends to blur this classification, since the maximum size of Ax for which AM can be perceived scales linearly with the size of the elements (Cavanagh et al 1985). (2) We observed that the higher the spatial density of the elements, the better the performance.…”

“…They reported that AM perception disappeared at equiluminan~ with RDC. If, however, successive frames of equiIuminant RDCs are not separated by dark inter-frame intervals, AM perception is stiil observed (Cavanagh et al, 1985). This observation, together with similar ones, contained in a comprehensive study of a wide range of AM phenomena, led Cavanagh and Mather (1990) to argue in favor of a single AM process, rather than the two separate (short-range and long-range) AM processes proposed earlier (Braddick, 1974, Pantle & Picciano, 1976.…”

The duration of 3-D form analysis in transformational apparent motion

“…Experiment 3B showed that form analysis at equiluminance takes approximately the same amount of time as under nonequiluminant conditions. TAM, unlike translational apparent motion (e.g., Cavanagh et al, 1985;Ramachandran et al, 1998), is not weakened under conditions of equiluminance.Whereas matching in translational apparent motion may depend primarily on motion energy, luminance contrast may be less important in TAM because matching here takes place on the basis of form relationships. Although the motion processing stream is generally thought to be primarily driven by changes in luminance contrast (e.g., Zeki, 1974), cells in MT respond to moving contours defined by equiluminantcolor and texture boundaries (Albright, 1992;Dobkins & Albright, 1994;Saito et al, 1989).…”

“…Real motion and translational apparent motion (e.g., Cavanagh, Boeglin, & Favreau, 1985;Ramachandran, Armel, Foster, & Stoddard, 1998) are weak at equiluminance. This experiment addressed whether TAM is perceived at equiluminance and whether form analysis can bias motion processing in this domain.…”

Color from Motion: Separate Contributions of Chromaticity and Luminance

“…In this case, we expected that the strength of the · subjective contour would be reduced or that it would not be seen at all. Luminance contrast is known to be critical for the formation of static subjective contours (Frisby and Clatworthy 1975;Gregory 1977), the perception of apparent motion (Ramachandran and Gregory 1978;Cavanagh et al 1985), and the perception of achromatic neon spreading (Bressan 1993 2.2.2 Procedure. Ten stimuli, varying in luminance and chromaticity of the test and surround dots as described above, were presented in random order.…”