一川 誠

We examined how the perceived simultaneity and temporal order of two visual stimuli depends upon the depth position of the stimuli specified by binocular disparity cue. When two stimuli were presented simultaneously at different depth positions in front of or around a fixation point, the observer perceived the more distance stimulus appeared before the nearer stimulus (Experiment 1). This illusory temporal order was found only for sudden stimulus presentation (Experiment 2). Similar tendency was found in the processing for motion-in-depth (Experiment 3). For the involuntary attention, which was caused by sudden presentation of a preceding stimulus, the effect of the preceding stimulus, which was presented in the depth space nearer than the fixation point, was larger than that of the stimulus, which was presented in the more distant space than the fixation point (Experiment 4). These results suggest that a common processing, which are related to the detection of the motion-in-depth underlies these bias in terms of the stimulus depth position, and therefore, that, in order to understand the basis of the perception of the simultaneity and temporal order, we have to clarify the temporal bias in the processing which are involved in conducting the experimental task.

The present paper demonstrates the significance of long-range inhibition in reaction-diffusion algorithms designed for edge detection and stereo disparity detection. In early visual systems, the long-range inhibition plays an important role in brightness perception. The most famous illusory perception due to the long-range inhibition is the Mach bands effect, which is observed in a visual system of an animal and also in the human visual system. The long-range inhibition also appears in the computer vision algorithm utilising the difference of two Gaussian filters for edge detection. Upon evidence implying analogy between brightness perception and stereo depth perception, several psychologists have suggested that; such the long-range inhibition works not only in the brightness perception, but also in the depth perception. We previously proposed biologically motivated reaction-diffusion algorithms designed for edge detection and stereo disparity detection. Thus, we show that the long-range inhibition also plays an important role in both of the reaction-diffusion algorithms through experimental study. Results of the study provide a new idea of improving performance of the reaction-diffusion stereo algorithm.

We used four experiments to examine how the perceived temporal order of two visual stimuli depends on the depth position of the stimuli specified by a binocular disparity cue. When two stimuli were presented simultaneously at different depth positions in front of or around a fixation point, the observer perceived the more distant stimulus before the nearer stimulus (Experiments 1 and 2). This illusory temporal order was found only for sudden stimulus presentation (Experiment 3). These results suggest that a common processing, which is triggered by sudden luminance change, underlies this illusion. The strength of the illusion increased with the disparity gradient and the disparity size (Experiment 4). We propose that this illusion has a basis in the processing of motion in depth, which would alert the observer to a potential collision with an object that suddenly emerges in front of the observer.

The present paper proposes a reaction-diffusion algorithm that detects edge positions and evaluates their strength. Edge strength refers to the sharpness of spatial brightness change at an edge position in image brightness distribution. The authors previously found that a discretised system derived from the FitzHugh-Nagumo reaction-diffusion equations spontaneously organises pulses at edge positions and works as an edge detector for binary images. Although the previous system has a merit in that it can detect edges having sharp corners, it is not applicable to grey level images or edge strength evaluation. The proposed algorithm utilises multiple systems, each of which consists of two subsystems of the reaction-diffusion equations coupled with a diffusion equation. The diffusion equation modulates a parameter value of the reaction-diffusion equations and helps to evaluate a level of edge strength. In addition, there is a connection between the two subsystems in each system; the connection helps to eliminates pseudo-pulses organised in the subsystems. Integration of the outputs of the multiple systems provides edge strength distribution. Finally, we apply the proposed algorithm to test images and confirm its performance.

The present paper proposes a visual integration algorithm that integrates intensity edge information into a stereo algorithm. The stereo algorithm assumes two constraints of continuity and uniqueness on disparity distribution. Since depth discontinuity around object boundaries does not satisfy the continuity constraint, it causes numerous errors in stereo disparity detection. In order to reduce the errors due to the depth discontinuity, we propose a new algorithm that integrates intensity edge information into the stereo algorithm. The stereo algorithm utilizes reaction-diffusion equations, in which diffusion coefficients control the continuity constraint. Thus, we introduce anisotropic diffusion fields into the reaction-diffusion equations; that is, we modulate the diffusion coefficients according to results of edge detection applied to image intensity distribution. We demonstrate how the proposed algorithm works around areas having depth discontinuity and confirm quantitative performance of the algorithm in comparison to other stereo algorithms.

Although previous studies have examined what kind of object arrangement could give observer beautiful impression, they have not achieved agreement. While some studies found observers' preference for the arrangements whose centroids were congruent with the center of the picture frame, the other studies found the observers' preference for the arrangement whose centroids were in the right side in the frame. The main purpose of this study is to solve this disagreement among previous studies. We conducted three experiments in which concreteness of the picture was manipulated, and observers rated their impression for the pictures with different centroid position. We used black circles (Experiment 1), concrete objects on white background (Experiment 2), and concrete objects on backgrounds of natural scenes (Experiment 3). Only in Experiment 3, we found that observers consistently preferred for the pictures whose centroid of the arrangement was in right side. Our results indicate that concreteness of the pictures caused the biased preferencefor the right side of the pictures.

A landscape photograph may give a different impression from that formed at the real scene, with respect to the size and distance of objects. Researchers have reported that the perceived sizes and distances of objects in a photograph are not identical to those in a real space. In order to develop a method to create a graphic image that is close to our visual impression as seen in the real space, two experiments were conducted. In Experiment 1, we examined how the magnification rate of the perceived size to the object size on the retina varied with the viewing distance (range was from 1 m to 10 m). In Experiment 2, we examined whether transformation based on the magnification rate is effective for creating an image that matches the perceived size of the object at the scene. Our results indicate that the magnification rate is useful for transforming the perspective image to match our perception of the objects regardless of the viewing distance.

In this study, we examined the spatial and temporal frequency tuning of motion-in-depth aftereffect. We changed the spatial frequency of test stimuli and temporal frequency of adapting stimuli to investigate the influence on the motion aftereffect duration. It was found that, in spite of the change of spatial frequency of test stimuli, the maximum motion aftereffect duration was measured when the mean temporal frequency of adapting stimuli was set to 3.83 Hz. On the other hand, in spite of the change of temporal frequency of adapting stimuli, the maximum motion aftereffect duration was measured when the mean spatial frequency of test stimuli was set to 0.40 cycles/degree. We also changed the moving direction of adapting stimuli in approaching and receding directions to investigate the moving direction influence on the motion aftereffect duration. It was noted that compared to the approaching motion, longer motion aftereffect duration was measured for the receding motion.

The present paper proposes an edge detection algorithm with the FitzHugh-Nagumo reaction-diffusion equations. The authors previously found that the discretized version of the reaction-diffusion equations organizes a static pulse at an edge position for a binary image or for a binarized image with a fixed threshold level. By finding static pulses from the result of the discretized version, we can detect edges. The algorithm proposed here furthermore detects edges from a gray-scale image. In order to handle the gray-scale image, the proposed algorithm computes a local average level of image brightness distribution with a simple diffusion equation and simultaneously utilizes the average level as the threshold level of the reaction-diffusion equations. That is, the local average level obtained by the simple diffusion equation modulates the threshold level of the reaction-diffusion equations. The proposed set of the reaction-diffusion equations coupled with the simple diffusion equation causes a pulse at a true edge position and also a pseudopulse at a pseudoposition. Thus, we additionally propose an algorithm that eliminates the pseudopulse and extracts the true one. We apply the proposed algorithm and a previous representative algorithm to well-known test images for confirming the validity of the proposed algorithm. © 2008 Pleiades Publishing, Ltd.

Psychological researchers have pointed out that as the distance between a viewer and an object increases, the perceived size of the object becomes larger than the size pre- dicted using the linear perspective. This phenomenon is called “size constancy”. The purposes of this study are to determine a magnification-rate function for rendering a graphic image to fit it with size and distance impressions obtained in real space obser- vation at a given distance, and to assess the validity of the magnification-rate function for computer graphic images. In the first experiment, we investigated the perceived size of an object placed at different distances, ranging from 1 to 10 m (short distance conditions), and from 4 to 120 m (long distance conditions). We found that the Z-ratio function (Thouless, 1931) can predict the perceived size for an object under the short distance conditions; however, it failed to predict the perceived size under the long dis- tance conditions. Therefore, we applied a logistic function to predict the perceived size of an object under both the short and long distance conditions. In the second experiment, we asked observers to rate the fit of the size and distance of a computer graphic image with the perceived size and distance of objects in a real space. The size and distance of objects in the graphic images were determined using the magnification- rate function in terms of the logistic function, or the conventional linear perspective. We found that the observers gave higher scores for the images generated using the magnification-rate function than those generated using the conventional linear perspec- tive. These results indicate that the magnification-rate function obtained in this study is more useful than the linear perspective in rendering computer graphic images to fit the size and distance of objects in the images with the real space observation.

In past studies on the neural transfer function, some researchers have taken both excitation and inhibition factors into consideration. However, these past models were based on the diffusion of substances between neighboring cells. Therefore, they are not suitable for considering excitation and inhibition factors in individual cells. In the present study, based on the physiological characteristics of synaptic transmission, we propose a new model in which facilitation and fatigue can be both considered in individual cells. Using the proposed model, the simulations of short-term memory, afterimage effect, motion aftereffect, Game of Life, and image feature detections were performed. We suggest that the proposed model is a valid and widely applicable neural model.

画家やデザイナーらは,色の軽重感によって視覚的に心地よいバランスとなるように2次元作品の配色を操作していると言われている.本研究では,視覚的に心地よいバランスとなる配色を行うために,色相,彩度,明度の軽重感への影響を客観的手法に基づいて理解することを目的とした.2つの実験において,マンセル表色系から選ばれた計65色の色票の軽重感をマグニチュード推定法により測定した.実験1では,色相の軽重感への影響を理解するために,無彩色とそれと同明度の有彩色(10色相)の軽重感を調べた.実験2では,彩度が軽重感におよぼす影響を理解するために,彩度の異なる色の軽重感を4色相において調べた.どちらの実験においても,明度が一定であっても色相や彩度が異なることで,軽重感が体系的に変化することが示された.以上の実験結果は,視覚的に心地よいバランスのとれた配色を行うには,色の3属性それぞれが軽重感に及ぼす影響を理解することが有効であることを示唆している.

In the past research on the neural transform model, some researchers took both excitation and inhibition factors into consideration. However, these past models relate to diffusion of the substance between neighboring cells, therefore these models are not rational for considering both excitation and inhibition factors in a separate cell. When repeated stimulation depolarizes a presynaptic axon terminal, the level of Ca2+ in the presynaptic axon terminal is increased. Thus, an increased number of quanta of transmitter are released. On the other hand, the release of the transmitter will result in the decrease in the quantity of the transmitter in the presynaptic axon terminal. Based on these physiology characteristics of synaptic transmission, we propose a new model in which facilitation and fatigue are both considered in a separate cell. Using the proposed model, short-term memory process, image feature detection and other image processing were simulated. We suggest that the proposed model is a valid and widely applicable neural model.

We investigated how observers' control of the stimulus change affects temporal aspects of visual perception. We compared the flash-lag effects for motion (Experiment 1) and for luminance (Experiment 2) under several conditions that differed in the degree of the observers' control of change in a stimulus. The flash-lag effect was salient if the observers passively viewed the automatic change in the stimulus. However, if the observers controlled the stimulus change by a computer-mouse, the flash-lag effect was significantly reduced. In Experiment 3, we examined how observers' control of the stimulus movement by a mouse affects the reaction time for the shape change in the moving stimulus and flash. Results showed that the control reduced the reaction time for both moving stimulus and flash. These results suggest that observers' manual control of the stimulus reduces the flash-lag effect in terms of facilitation in visual processing. (c) 2006 Elsevier Ltd. All rights reserved.

In two experiments, we investigated how the number of auditory stimuli affected the apparent motion induced by visual stimuli. The multiple visual stimuli that induced the apparent motion on the front parallel plane, or in the depth dimension in terms of the binocular disparity cue, were accompanied by multiple auditory stimuli. Observers reported the number of visual stimuli (Experiments 1 and 2) and the displacement of the apparent motion that was defined by the distance between the first and last visual stimuli (Experiment 2). When the number of auditory stimuli was more/less than that of the visual stimuli, observers tended to perceive more/less visual stimuli and a larger/smaller displacement than when the numbers of the auditory and visual stimuli were the same, regardless of the dimension of motion. These results suggest that auditory stimulation may modify the visual processing of motion by modulating the spatiotemporal resolution and extent of the displacement.

We have investigated how effectively the training of basic design can facilitate student&#039;s interest in the areas of science and mathematics. It has been pointed out for these several years that students in elementary and high school avoid scientific classes. We had tried to find new methods and materials which can induce a link between design, science and mathematics. We had model classes for students from an elementary school and students from a junior high school in order to examine the effect of training for basic design in mathematics and science. The results of the analyses on the student&#039;s answers suggest that the training of basic design, in particular observing natural objects, and drawing geometric shapes, may promote the motivation to learn mathematics and science for students in both elementary school and junior high school.<br />

Pinna and Brelstaff (2000 Vision Research 40 2091 - 2096) reported a motion illusion on viewing two concentric circles consisting of quadrangular components with black and white sides on a grey background. Our results suggest that the illusion is based on the integration of motion signals derived from oblique components, and on the consistency in the direction among those components. Furthermore, arrays of these oblique components can elicit the perception of motion not only for the oblique components themselves, but also for other objects in the picture. We propose that the motion illusion depends not only upon detection of the illusory motion signal at each local oblique component, but also upon the accumulation of the signal all over the stimulus configuration.

Pinna and Brelstaff (2000 Vision Research 40 2091 - 2096) reported a motion illusion on viewing two concentric circles consisting of quadrangular components with black and white sides on a grey background. Our results suggest that the illusion is based on the integration of motion signals derived from oblique components, and on the consistency in the direction among those components. Furthermore, arrays of these oblique components can elicit the perception of motion not only for the oblique components themselves, but also for other objects in the picture. We propose that the motion illusion depends not only upon detection of the illusory motion signal at each local oblique component, but also upon the accumulation of the signal all over the stimulus configuration.

The present paper proposes a method that estimates a stereo disparity map. The method consists of multilayered networks of reaction-diffusion equations having activator and inhibitor variables. A particular set of equations describes non-linear oscillators coupled with diffusion processes, and governs a disparity layer. Estimating a stereo disparity map requires the two main constraints: the smoothness constraint and the uniqueness. The activation process of the diffusion-coupled oscillators performs the filling-in process for a stereo disparity map as the smoothness constraint. The mutual inhibition mechanism among the multilayered networks retains the uniqueness constraint of the disparity at a particular pixel site. By applying the proposed equations to cross-correlation functions derived from stereo images, we obtain a self-organized stereo disparity map. Experimental results show that the proposed method is superior to a previous one, in particular, for real stereo images.

This study examined a method of using a masking sound to improve the impression of an environment with noise. In three experiments, we presented a masking sound of several types of music, or pink noise, with road traffic noise, or white noise, and the participants evaluated the unpleasantness and restlessness of the environment. Regardless of the type of noise, the impression of the environment was improved when we presented relaxing and well known music with higher sound level (L_&lt;eq&gt;) than that of the noise. The improvement was greater when there was a large difference in the sound level ...

The present paper proposes a system that detects a stereo disparity map from random-dot stereograms with the grouping process. A simple operation for random-dot stereograms converts the stereo correspondence problem to the segmentation one. For solving the segmentation problem derived from random-dot stereograms, the stereo vision system proposed here utilizes the grouping process of our previously proposed model. The model for the grouping process consists of multiple reaction-diffusion models, each of which governs segments having a disparity in the stereo vision system. A self-inhibition mechanism due to strong inhibitory diffusion within a particular reaction-diffusion model and a mutual-inhibition mechanism among the models are built in the proposed system. Experimental results for artificially generated random-dot stereograms show the validity of the proposed system.

We examined whether depth perception was produced by the parallax of second-order motion (i.e., movement of non-luminance features, such as flicker, texture size modulation, or contrast modulation that moved in synchrony with lateral head movement). The results, obtained with second-order motion from a simple grating stimuli, showed that depth order was judged correctly with probabilities well above chance, but the reported depth magnitude did not co-vary with parallax magnitude. When we used a complex spatial pattern for which feature tracking was difficult, the accuracy of depth-order judgments descended to chance level. Our results suggest that the visual system (a) can detect the correct depth order by tracking a relative shift in the salient features of a stimulus pattern, but (b) cannot determine depth magnitude from a velocity field given by second-order-motion stimuli. (C) 2004 Elsevier Ltd. All rights reserved.

We examined the dependency of the integration of multiple depth cues upon the combined cues and upon the consistency of depth information from different cues. For each observer, depth thresholds were measured by the use of stimuli in which different depth cues (motion parallax, binocular disparity, and monocular configuration) specified the surface undulating sinusoidally with different spatial frequencies and different phases. Analysis of d' showed that the performance was better than the prediction of probability summation only when parallax and disparity cues specified an undulation with the same spatial frequency and same phase. The probability summation model overestimated the performance for the other conditions of combination of disparity and parallax, and for all of the conditions of combination of disparity and monocular configuration. These results suggest that the improvement in depth perception caused by integration of multiple cues depends on the type of combined cues, and that the visual system possibly integrates the depth information from different cues at different stages of the visual processing. (C) 2003 Elsevier Ltd. All rights reserved.

The present paper proposes a computational model for the realization of visual functions of edge and/or feature detection and segmentation. The model utilizes a reaction-diffusion model which is an extended version of the diffusion-based Difference of Gaussians (DOG) filter previously proposed by Marr and Hildreth as an edge detection model. The proposed model self-organizes spatial patterns having edges and/or features and segments. These patterns are sustained by the intrinsic mechanism of the proposed model under specific conditions. In addition, the model also helps to solve the stereo matching problem in random dot stereograms and the aperture problem in optical flow computation. These Visual functions of the proposed model are demonstrated with both artificial and real images.

The method of psychological active control, in which a neutral or pleasant sound(masking sound)is superimposed on an unpleasant sound, is effective in increasing the pleasantness of the auditory environment. In present study, we examined the effects of presenting a masking sound with a motion picture in psychological active control. We presented a type of masking sound(music)and one of the three types of motion pictures(road traffic picture, dynamic noise, natural picture)with one of the two types of noise sounds(road traffic noise, white noise). Presenting road traffic picture with road traffic noise, and natural picture with white noise, reduced the unpleasantness of the noise sounds. These results suggest that presenting motion picture with masking sound is effective in increasing the pleasantness of environment. This effect was restricted to the case in which the pictures are situationally matched with the noise sounds. Also, our results showed that the effect depends on the level of noise sound.

For 35 to 39 days, four observers wore continuously left-right reversing spectacles which pseudoscopically reverse the order of binocular disparity and direction of convergence. In three tests, we investigated how the visual system copes with the transformation of depth and distance information due to the reversing spectacles. In stereogram observation, after a few days of wearing the spectacles, the observers sometimes perceived a depth order which was opposite to the depth order that they had perceived in the pre-spectacle-wearing period. Monocular depth cues contributed more to depth perception in the spectacle-wearing period than they did in the pre-spectacle-wearing period. While the perceived distance significantly decreased during the spectacle-wearing period, we found no evidence of adaptive change in distance perception. The results indicate that the visual system adapts itself to the transformed situation by not only changing the processing of disparity but also by changing the relative efficiency of each cue in determining apparent depth.

The human visual system has the grouping mechanism, which groups the pixel sites sharing similar features. The mechanism works for several kinds of features, such as, texture pattern, orientation, motion, etc. The present paper proposes a model realizing the perceptual grouping mechanism on the feature of orientation. A reaction-diffusion model describes pattern formation processes in biological and chemical systems. The proposed model utilizes the multi-sets of biologically motivated reaction-diffusion models, each of which consists of two equations having activator and inhibitor variables. A particular set organizes groups sharing similar orientation. The activator variable of each set extends its corresponding groups, it inhibits other groups from extending at boundaries between different groups. In addition, the inhibitor variable of each set inhibits itself from extending. Through analysis of artificial and real images, it is confirmed that the activation and inhibition mechanisms are necessary for the realization of the grouping mechanism.

We investigated how the direction of the three dimensional movement of computer graphics affect the observer&#039;s impression, especially the impression of pleasure. Our stimuli were motion pictures consisted of 50 spheres presented in a display. The spheres moved in one of eight directions(45 deg step from upward direction)with the velocity of about 1 cm/sec. Two-dimensional motion pictures consisted of discs were also presented as a comparison. In the experiment 1, 28 observers chose the most and least pleasant direction. Observers had the most pleasant impression when they felt the upward movement of themselves while they had the most unpleasant impression when they felt the downward movement of themselves. We didn&#039;t find such results for two-dimensional stimuli. In the experiment 2, 40 observers estimated their impression in terms of SD method. A factor analysis on the results of second experiment found four factors; powerfulness, evaluation, airiness, and reality. The pleasantness was strongly related to the evaluation factor. The results suggested that the downward movement exaggerates the impression of powerfulness and reality and eliminates the impression of airiness, and that the impression of pleasantness depends upon the perception of observer&#039;s own vertical movement (vertical vection).

We investigated the interaction between motion parallax and binocular disparity cues in the perception of surface shape and depth magnitude by the use of the random dot stimuli in which these cues specified sinusoidal depth surfaces undulating with different spatial frequencies. When ambiguous motion parallax is inconsistent with unambiguous disparity cue, the reasonable solution for the visual system is to convert the motion signal to the flow on the surface specified by disparity. Two experiments, however, found that the visual system did not always use this reasonable solution observers often perceived the surface specified by a composite of the two cues, or the surface specified by parallax alone. In the perception of this composite of the two cues, the apparent depth magnitude increased with the increase of the depth magnitude specified by both cues. This indicates that the visual system can combine the depth magnitude information from parallax and disparity in an additive fashion. The interference with parallax by disparity implies that the parallax processing is not independent of the disparity processing.

We examined how the consistency of depth information from motion parallax and binocular disparity cues affects the interaction of these cues at near threshold level. For five adult observers, depth thresholds were measured by the use of stimuli in which motion and/or stereo cues specified the sinusoidal undulation with different spatial frequencies and different phases. Depth sensitivity was found to change only if these cues specified an undulation with the same spatial frequency: depth sensitivity was elevated when two cues specified an undulation with the same phase, while it declined when these cues specified an undulation in counter-phase. These results suggest that the processing of these cues is founded on a common mechanism in which motion and stereo cues interact in accordance with the consistency of the surface shape and depth order of the undulation specified by each cue.

Two experiments presented motion disparity conflicting with binocular disparity to examine how these cues determined apparent depth order (convex, concave) and depth magnitude. In each experiment, 8 subjects estimated the depth order and depth magnitude. The first experiment showed the following. (1) The visual system used one of these cues exclusively in selecting a depth order for each display. (2) The visual system integrated the depth magnitude information from these cues by a weighted additive fashion if it selected the binocular disparity in depth order perception and if the depth magnitude specified by motion disparity was small relative to that specified by binocular disparity. (3) The visual system ignored the depth magnitude information of binocular disparity if it selected the motion disparity in depth order perception. The second experiment showed that these three points were consistent whether the subject's head movement or object movement generated motion disparity.

The plasticity of binocular depth perception was investigated. Six subjects wore left-right reversing spectacles continuously for 10 or 11 days. On looking through the spectacles, the relation between the direction of physical depth (convex or concave) and the direction of binocular disparity (crossed or uncrossed) was reversed, but other depth cues did not change. When subjects observed stereograms through a haploscope and were asked to judge the direction of perceived depth, the directional relation between perceived depth and disparity was reversed both in the two line-contoured stereograms and in the random-dot stereogram in the middle of the wearing period, but the normal relation often returned late in the wearing period. When subjects observed two objects while wearing the spectacles and were asked which appeared the nearer, veridical depth perception increased as the wearing-time passed. These results indicate that the visual transformation reversing the direction of binocular disparity causes changes both in binocular stereopsis and in processes integrating different depth cues.

Binocular stereopsis is more sluggish in processing the binocular disparity representing a horizontal slant in depth (compression disparity) than in processing that representing a vertical slant in depth (shear disparity). We examined this anisotropic sensitivity in binocular stereopsis by using random dot streograms representing depth surfaces slanted in different orientations. In Experiment 1 and 2, we found that the latency to depth perception depended on the combinational rate of the compression disparity and shear disparity. In Experiment 3, it was found that there was a selective adaptation which reduced the sensitivity of stereoscopic depth perception in terms of the disparity types (compression or shear). These results suggest that there are two processes with different sensitivities, one tuned to the compression disparity and the other to the shear disparity, and that the cooperation of these two processes decides the sensitivity of binocular stereopsis to a disparity representing a certain slant in depth.