We have been measuring the eye movements using several kinds of random-dot, stereograms(RDSs) and analyzing. However, these RDSs Were composed of simple disparity and simple perceptional area (uneven area). Therefore, we could easily achieve the state of stereopsis. In this study, we used RDSs With horseshoe shape as the perceptional area. Then, we presented the RDS moved or deformed upto stereopsis limits to a subject. These are cases of only left RDS is rotated ±15 degrees, brought down,or magnify. We analyzed subject's response, eye movement and viewing points. As the results, we could obtain limit values for several displacements or deformations of RDS.
Two experiments were designed to investigate the mechanism of the chromatic induction. In Exp. 1, the color discrimination thresholds for a white stimulus surrounded with an inducing color stimulus (red, purple, violet, blue, greenish blue, green, yellowish green, greenish yellor or yellow) were detemined along 8 color axes. The thresholds were compared with the thresholds for a white stimulus without the inducing stimulus. The inducing color stimulus caused the elevation of the color discrimination thresholds along the inducing-complementary direction, but did not along the orthogonal axis to the inducing-complementary axis. In Exp. 2, color discrimination thresholds for a without-inducing stimulus apparently similar as the white stimulus surrounded with the color inducing stimulus were determined along the 8 color axes. Comparison of the results in Exps. 1 and 2 suggested that the simultaneous color induction may be mediated by a different mechanism from the color opponent process.
After adapting to a grating pattern, the detection threshold and the apparent contrast for a sinusoidal test grating were determined as a function of spatial frequency. For the threshold performance, the contrast thresholds were selectively elevated after the grating adaptation. The threshold elevation was observed only within the spatial frequency range of 1 octave above the adaptation frequency. On the other hand for the supra-threshold performance the reduction of apparent contrast as a function of the test frequency showed different functional form depending on the contrast level. The results suggest the existence of two mechanisms which control the sensitivities of spatial-frequency-selective channels. One is the within-mechanism which may control the threshold of individual channel. showing a narrow-band property. The other is the between-mechanism which may control the gain of channel means of a mutual inhibition among different channels.
Using the sequential presentation of dark disks with a sector removed, the effects of their SOAs and luminance contrasts on the percept of illusory contours(ICs) were investigated. Two experiments were conducted: one was to assess the threshold of inducer's contrast for the percept of ICs, as a function of SOA between inducers, the others was to assess the strength of ICs as a function of SOA between inducers and their contrast. At the threshold-level strength of IC, little or no temporal summation of the inducer's contrast occurred. Above the threshold-level strength, the temporal summation effects increased with the strength of IC.
One of the properties of the human visual system is its pre-attentive texture discrimination capability. The human visual system can perceive textual differences almost instantaneously and effortlessly. It has been hypothesized that pre-attentive texture discrimination are based on a few local conspicuous features(textons). We propose a coupled Markov random field with two layers as a computational model for the texton-based pre-attentive texture segmentation. The model prameters are estimated and the segmentation is carried out iteratively.