Biomedical subjects

Vincent J Chen

Publications and source records attributed to Vincent J Chen.

3 recordsLinked to original sources

PubMed2006

Vernier acuity of illusory contours defined by motion.

We present here a series of experiments exploring a special class of visual completion that is strictly tied to the perception of apparent motion. The stimuli consist of sparse random-dot arrays, in which dots remain in place. Changes of luminance or color of the dots at leading and trailing edges of an apparently moving region are integrated over space and time to produce the perception of well-defined contours, shapes, and color. We test how Vernier acuity of apparent motion-defined illusory bars depends on speed, density, and stimulus configurations. We found that higher speed of apparent motion reduces the Vernier acuity thresholds. These thresholds also decrease with increasing density of dots, whose luminance changes provide the apparent motion signal required for the perception of illusory contours. In subsequent experiments, we showed that luminance-defined flankers could seamlessly integrate with and improve the perception of apparent motion-defined contours, reducing their Vernier thresholds.

Color↗

PubMed2002

Depth from subjective color and apparent motion.

We report that color and depth, as well as form, are recovered in tandem with seeing motion. The stimulus, consisting of multiple frames, was designed to keep all aspects, except color, of the binocular images identical. In still view, rivalry occurs due to the unmatched color of some corresponding image elements in the two eyes. When frames--created by translating color assignments and nothing else--are rapidly cycled, a colored object is seen moving in depth. In natural scenes the same mechanisms may be used to reconstruct depth, color, and form of hidden objects so that they can be seen as if in plain view.

Color Perception↗

PubMed2002

Subjective color from apparent motion.

In an effect we call color from motion (CFM), apparent motion is accompanied by subjective color spread seen in physically achromatic regions. Here we report that physical lights can cancel the subjective color seen in CFM. As measured by cancellation, the saturation of the subjective color spread increases as the luminance of the test elements increase. Without luminance differences between test and surround elements, chromaticity differences alone can result in the perception of subjective color spread. In this case, subjective color spread is seen without seeing a subjective contour, suggesting that CFM does not require contour formation and that color - independent of contour - can be recovered in tandem with seeing motion. There are two modes in which CFM is perceived, either (1) as a localized change of illumination, a colored spotlight or shadow, moving over a textured surface or (2) as a moving, colored object seen through holes in an occluding surface. The mode in which CFM is seen depends on figural cues and on regional differences in luminance contrast between the chromatic elements and the achromatic background. Regions with distinct figural cues are always seen as moving; and CFM is seen in the first mode if the regions are of lower luminance contrast and in the second mode if the regions are of higher luminance contrast. Without figural cues, the regions of lower luminance contrast are always seen to move and CFM is seen in the first mode.

Color Perception↗