Biomedical subjects

B G Khang

Publications and source records attributed to B G Khang.

3 recordsLinked to original sources

PubMed2000

Apparent swinging motion from a 2-D sinusoidal pattern.

A new motion illusion is reported that is observed on a 2-D sinusoidal pattern composed of two 1-D sinusoids, in which the constituent elements of the middle column appear to swing relative to the two flanking columns when the point of fixation is slowly moved back and forth about the middle column. To better understand the underlying mechanisms of the apparent swinging motion, the spatial properties of a 2-D sinusoidal pattern were examined in terms of spatial frequency, orientation, and contrast. Thirty-four subjects rated the magnitude of the motion. The apparent swinging was greatest when the two 1-D components had spatial frequencies of 1-2 cycles deg-1, relative orientations between 15 degrees and 30 degrees, and high contrasts. A spatiotemporal interaction between spatially overlapping visual units differing in polarity (Khang and Essock, 1997 Perception 26 585-597, 831-846) and the resultant shift in the global-motion signal was proposed as a likely cause of the apparent swinging motion.

Contrast Sensitivity↗

PubMed1997

A motion illusion from two-dimensional periodic patterns.

The spatial properties of a motion illusion (the Ouchi illusion) that occurs in a stationary pattern were examined by means of a variety of two-dimensional periodic patterns (formed by multiplying pairs of various one-dimensional periodic functions). In two experiments, observers rated the magnitude of the illusion. The results showed that (1) patterns having large energy and steep saddle-shaped contrast gradients tended to generate stronger illusions, (2) the composite pattern made up of the sum of the fundamental and harmonic components exhibited a stronger illusion than either the fundamental or the harmonic pattern, (3) patterns possessing an element orientation and phase shift similar to those of a rectangular checkerboard, and with element sizes of 15-50 min in width and 4-8 min in height yielded a larger illusion, (4) equiluminant colors largely abolished the effect, and (5) blurring the boundary between the test and surround did not reduce the illusion. Interactions between spatially overlapping ON and OFF units was discussed as a possible underlying cause of this phenomenon.

Humans↗

PubMed1997

Apparent relative motion from a checkerboard surround.

To better understand the Ouchi illusion in which a stationary picture generates illusory relative motion, the spatial properties of the constituent elements of the rectangular checkerboard background were examined. Results of experiment 1 revealed that the largest illusion was obtained with elements of approximately 20-30 min in width and 4-6 min in height, an orientation of the constituents that was orthogonal to that of the test grating, and a phase shift of the alternate stripes that was close to 180 degrees. In experiment 2 it was found that the illusion increased in magnitude with increasing achromatic contrast but was minimal with a pattern of high chromatic contrast near isoluminance. In experiment 3, two test patches were presented simultaneously in the checkerboard background and were varied independently in their orientation to explore whether or not their motions were perceived as coherent (common fate). Patches having identical orientations, and nearly orthogonal to the surround, were synchronized more strongly than those having reflected orientations. Hysteresis related to the gain control of spatially overlapping visual units differing in their polarity (ON/OFF) was discussed as a possible cause of this phenomenon.

Contrast Sensitivity↗