Spatial Accuracy of Predictive Saccades Determines the Performance of Continuous Visuomotor Action

In a table tennis rally, players perform interceptive actions on a moving ball continuously in a short time, such that the acquisition process of visual information is an important determinant of the performance of the action. However, because it is technically hard to measure gaze movement in a real game, little is known about how gaze behavior is conducted during the continuous visuomotor actions and contributes to the performance. To examine these points, we constructed a novel psychophysical experiment model enabling a continuous visuomotor task without spatial movement of any body parts, including the arm and head, and recorded the movement of the gaze and effector simultaneously at high spatiotemporal resolution. In the task, Gabor patches (target) moved one after another at a constant speed from right to left at random vertical positions on an LC display. Participants hit the target with a cursor moving vertically on the left side of the display by controlling their prehensile force on a force sensor. Participants hit the target with the cursor using a rapid-approaching movement (rapid cursor approach, RCA). Their gaze also showed rapid saccadic approaching movement (saccadic eye approach, SEA), reaching the predicted arrival point of the target earlier than the cursor. The RCA reached in or near the Hit zone in the successful (Hit) trial, but ended up away from it in the unsuccessful (Miss) trial, suggesting the spatial accuracy of the RCA determines the task's success. The SEA in the Hit trial ended nearer the target than the Miss trial. The spatial accuracy of the RCA diminished when the target disappeared 100 ms just after the end of the SEA, suggesting that visual information acquired after the saccade acted as feedback information to correct the cursor movement online for the cursor to reach the target. There was a target speed condition that the target disappearance did not compromise RCA's spatial accuracy, implying the possible RCA correction based on the post-saccadic gaze location information. These experiments clarified that gaze behavior conducted during fast continuous visuomotor actions enables online correction of the ongoing interceptive movement of an effector, improving visuomotor performance.

Perceptual judgments for the softness of materials under indentation

Humans can judge the softness of elastic materials through only visual cues. However, factors contributing to the judgement of visual softness are not yet fully understood. We conducted a psychophysical experiment to determine which factors and motion features contribute to the apparent softness of materials. Observers watched video clips in which materials were indented from the top surface to a certain depth, and reported the apparent softness of the materials. The depth and speed of indentation were systematically manipulated. As physical characteristics of materials, compliance was also controlled. It was found that higher indentation speeds resulted in larger softness rating scores and the variation with the indentation speed was successfully explained by the image motion speed. The indentation depth had a powerful effect on the softness rating scores whose variation with the indentation depth was consistently explained by motion features related to overall deformation. Higher material compliance resulted in higher rating scores while their effect was not straightforwardly explained by the motion features. We conclude that the brain makes visual judgments about the softness of materials under indentation on the basis of the motion speed and deformation magnitude while motion features related to material compliance require further study.

Color Layer Scissioning in See-Through Augmented Reality

Color appearance of transparent objects is not adequately described by colorimetry or color appearance models. Despite the fact that the retinal projection of a transparent object is a combination of its color and the background, measurements of this physical combination fail to predict the saliency with which we perceive the object's color. When the perceive color forms in the mind, awareness of their physical relationship separates the physical combination into two unique perceptions. This is known as color scissioning. In this paper a psychophysical experiment utilizing a seethrough augmented reality display to compare virtual transparent color samples to real color samples is described and confirms the scissioning effect for lightness and chroma attributes. A previous model of color scissioning for AR viewing conditions is tested against this new data and does not satisfactorily predict the observers' perceptions. However, the model is still found to be a useful tool for analyzing the color scissioning and provides valuable insight on future research directions.

The threshold of color inconstancy

Color inconstancy refers to significant changes in the perceived color of an object across two or more different lighting conditions, such as daylight and incandescent light. This research focusses on defining the threshold of color inconstancy between generated D65 and A illumination through a psychophysical experiment. Although modern color appearance models provide equations to calculate the degree of adaptation, a neutral grey match experiment was completed to produce a more accurate D values for the experimental viewing conditions. Like setting an instrumental color tolerance experiment, a second, sorting, experiment was used to define the threshold of color inconstancy. This threshold is the color shift, expressed in color difference terms, required for observers to notice a color change across changes in illumination. In addition, the tolerance ellipsoid for each Munsell principal hue group was also established.

Effects of Display and Ambient Illuminance on Visual Comfort for Reading on a Mobile Device

A psychophysical experiment was carried out to investigate visual comfort when reading on three OPPO Find X3s displays at three luminance levels (100, 250 and 500 cd/m2) at five illuminance levels (0, 10, 100, 500 and 1000 lx). Twenty young observers evaluated visual comfort using a 6-category points method. The results showed that observers felt most comfortable at the illuminance of 500 lx or display luminance of 500 cd/m2. There was an interaction between ambient illuminance and display luminance. High ambient light and display brightness levels provide a more pleasant visual experience. In low ambient light, however, the lower the brightness level, the more comfortable it is to see. Regarding the influence of background colour on visual comfort, the observers felt more comfortable having a grey background than white or black colour. When at dim illuminance, the background colour would have a great influence on visual comfort for negative contrast conditions, but when at higher illuminance, different background lightness levels had a great impact on visual comfort for positive contrast conditions. The above findings are very similar to the display luminance levels of 100 and 250 cd/m2.

Time course chromatic adaptation under highly saturated illuminants

The goal of this study was to investigate the time course characteristics of chromatic adaptation under highly saturated illuminants. A psychophysical experiment with neutral matching method was conducted on a mobile display at different luminance levels. Models of chromatic adaptation degree against duration of time were fitted using a proportional rate growth function. The upper limit and growth rate of adaptation degree were studied. It was found that higher adapting luminance and lower display luminance led to higher degree and faster speed of chromatic adaptation. This study also proposed the time to achieve stable chromatic adaptation.

Models to predict naturalness and image quality for images containing three memory colors: sky, grass, and skin

When evaluating the image quality, people mostly would like to concentrate on the color appearance of memory objects, representing the naturalness and reality of the image scene. Generally, an image with objects which have perfect memory colors reproduction will give natural and harmonious feelings. Many previous studies had proved the critical role of naturalness in image quality assessment, but it was still tough to scale the image naturalness precisely. In this study, natural images with blue sky, green grass, and skin colors were selected and partially rendered to develop the model of preference and naturalness of typical memory colors. A psychophysical experiment was conducted to collect the visual data of these images. Afterward, the psychophysical data were used to build the preference models and naturalness models, respectively. The models were then compared with previous studies. Results showed that the new models could accurately predict the preference and naturalness of target memory colors.

A study on Memory Colours

Memory colour has generated a sustained interest in the colour world. Previous studies mainly focused on the reflection colour chips and colour samples on real scenes or displays. Less attention was paid to the specific attributes of memory colour. In this paper, the forced choice psychophysical experiment method was used to study the preference, the colourfulness and the naturalness memory colours of 29 familiar objects on mobile displays by Chinese observers. The experiment collected the memory colours data and the representative memory colour was specified by CIELAB L*, a*, b* value. The intra-observer and inter-observer variations were analyzed by mean colour difference from the mean values, which was compared with other similar studies. An ellipsoid model was established to represent results in terms of memory colour centre and colour range in CIELAB a* b* space. At the same time, the results of this experiment were compared with those of previous experiments.

Thermal Tactile Perception

Using thermal tactile sensing mechanism based on semi-infinite body model, and combining with the advantages of maximum proportional controller, fuzzy and PID controller, a thermal tactile perception and reproduction experiment device (TTPRED) was designed based on the composite control strategy of threshold switching. The finger difference threshold measurement experiment of thermal tactile was carried out and the finger thermal tactile difference threshold was measured. The relationship between thermal tactile sensation and emotion based on temperature cues has been explored. The experiment results show that, the temperature control range of TTPRED is from -10℃ to 130℃, the temperature resolution and precision are 0.01℃ and ±0.1℃ respectively, the maximum heating or cooling rate is greater than 12℃, and the TTPRED can realize the temperature output of the specific waveform quickly and accurately. The experiment results of psychophysical experiment will provide the experimental foundations and technical support for the further study of thermal tactile perception and reproduction.

Thermal Tactile Perception

Using thermal tactile sensing mechanism based on semi-infinite body model, and combining with the advantages of maximum proportional controller, fuzzy and PID controller, a thermal tactile perception and reproduction experiment device (TTPRED) was designed based on the composite control strategy of threshold switching. The finger difference threshold measurement experiment of thermal tactile was carried out and the finger thermal tactile difference threshold was measured. The relationship between thermal tactile sensation and emotion based on temperature cues has been explored. The experiment results show that, the temperature control range of TTPRED is from -10℃ to 130℃, the temperature resolution and precision are 0.01℃ and ±0.1℃ respectively, the maximum heating or cooling rate is greater than 12℃, and the TTPRED can realize the temperature output of the specific waveform quickly and accurately. The experiment results of psychophysical experiment will provide the experimental foundations and technical support for the further study of thermal tactile perception and reproduction.