ACM Transactions on Applied Perception最新文献

Electrovibration is used in touch enabled devices to render different textures. Tactile sub-modal stimuli can enhance texture perception when presented along with electrovibration stimuli. Perception of texture depends on the threshold of electrovibration. In the current study, we have conducted a psychophysical experiment on 13 participants to investigate the effect of introducing a subthreshold electrotactile stimulus (SES) to the perception of electrovibration. Interaction of tactile sub-modal stimuli causes masking of a stimulus in the presence of another stimulus. This study explored the occurrence of tactile masking of electrovibration by electrotactile stimulus. The results indicate the reduction of electrovibration threshold by 12.46% and 6.75% when the electrotactile stimulus was at 90% and 80% of its perception threshold, respectively. This method was tested over a wide range of frequencies from 20 Hz to 320 Hz in the tuning curve, and the variation in percentage reduction with frequency is reported. Another experiment was conducted to measure the perception of combined stimuli on Likert’s scale. The results showed that the perception was more inclined towards the electrovibration at 80% of SES and was indifferent at 90% of SES. The reduction in the threshold of electrovibration reveals that the effect of tactile masking by electrotactile stimulus was not prevalent under subthreshold conditions. This study provides significant insights into developing a texture rendering algorithm based on tactile sub-modal stimuli in the future.

We investigate the optimal aesthetic location and size of a single dominant salient region in a photographic image. Existing algorithms for photographic composition do not take full account of the spatial positioning or sizes of these salient regions. We present a set of experiments to assess aesthetic preferences, inspired by theories of centeredness, principal lines, and Rule-of-Thirds. Our experimental results show a clear preference for the salient region to be centered in the image and that there is a preferred size of non-salient border around this salient region. We thus propose a novel image cropping mechanism for images containing a single salient region to achieve the best aesthetic balance. Our results show that the Rule-of-Thirds guideline is not generally valid but also allow us to hypothesize in which situations it is useful and in which it is inappropriate.

A foveated image can be entirely reconstructed from a sparse set of samples distributed according to the retinal sensitivity of the human visual system, which rapidly decreases with increasing eccentricity. The use of generative adversarial networks (GANs) has recently been shown to be a promising solution for such a task, as they can successfully hallucinate missing image information. As in the case of other supervised learning approaches, the definition of the loss function and the training strategy heavily influence the quality of the output. In this work,we consider the problem of efficiently guiding the training of foveated reconstruction techniques such that they are more aware of the capabilities and limitations of the human visual system, and thus can reconstruct visually important image features. Our primary goal is to make the training procedure less sensitive to distortions that humans cannot detect and focus on penalizing perceptually important artifacts. Given the nature of GAN-based solutions, we focus on the sensitivity of human vision to hallucination in case of input samples with different densities. We propose psychophysical experiments, a dataset, and a procedure for training foveated image reconstruction. The proposed strategy renders the generator network flexible by penalizing only perceptually important deviations in the output. As a result, the method emphasized the recovery of perceptually important image features. We evaluated our strategy and compared it with alternative solutions by using a newly trained objective metric, a recent foveated video quality metric, and user experiments. Our evaluations revealed significant improvements in the perceived image reconstruction quality compared with the standard GAN-based training approach.

Eye tracking studies have shown that reading code, in contradistinction to reading text, includes many vertical jumps. As different lines of code may have quite different functions (e.g., variable definition, flow control, or computation), it is important to accurately identify the lines being read. We design experiments that require a specific line of text to be scrutinized. Using the distribution of gazes around this line, we then calculate how the precision with which we can identify the line being read depends on the font size and spacing. The results indicate that, even after correcting for systematic bias, unnaturally large fonts and spacing may be required for reliable line identification.

Interestingly, during the experiments, the participants also repeatedly re-checked their task and if they were looking at the correct line, leading to vertical jumps similar to those observed when reading code. This suggests that observed reading patterns may be “inefficient,” in the sense that participants feel the need to repeat actions beyond the minimal number apparently required for the task. This may have implications regarding the interpretation of reading patterns. In particular, reading does not reflect only the extraction of information from the text or code. Rather, reading patterns may also reflect other types of activities, such as getting a general orientation, and searching for specific locations in the context of performing a particular task.

Ultrasound mid-air haptic (UMH) devices are a novel tool for haptic feedback, capable of providing localized vibrotactile stimuli to users at a distance. UMH applications largely rely on generating tactile shape outlines on the users’ skin. Here we investigate how to achieve sensations of continuity or gaps within such two-dimensional curves by studying the perception of pairs of amplitude-modulated focused ultrasound stimuli. On the one hand, we aim to investigate perceptual effects that may arise from providing simultaneous UMH stimuli. On the other hand, we wish to provide perception-based rendering guidelines for generating continuous or discontinuous sensations of tactile shapes. Finally, we hope to contribute toward a measure of the perceptually achievable resolution of UMH interfaces. We performed a user study to identify how far apart two focal points need to be to elicit a perceptual experience of two distinct stimuli separated by a gap. Mean gap detection thresholds were found at 32.3-mm spacing between focal points, but a high within- and between-subject variability was observed. Pairs spaced below 15 mm were consistently (>95%) perceived as a single stimulus, while pairs spaced 45 mm apart were consistently (84%) perceived as two separate stimuli. To investigate the observed variability, we resort to acoustic simulations of the resulting pressure fields. These show a non-linear evolution of actual peak pressure spacing as a function of nominal focal point spacing. Beyond an initial threshold in spacing (between 15 and 18 mm), which we believe to be related to the perceived size of a focal point, the probability of detecting a gap between focal points appears to linearly increase with spacing. Our work highlights physical interactions and perceptual effects to consider when designing or investigating the perception of UMH shapes.

Extended reality (XR) technologies, such as virtual reality (VR) and augmented reality (AR), provide users, their avatars, and embodied agents a shared platform to collaborate in a spatial context. Although traditional face-to-face communication is limited by users’ proximity, meaning that another human’s non-verbal embodied cues become more difficult to perceive the farther one is away from that person, researchers and practitioners have started to look into ways to accentuate or amplify such embodied cues and signals to counteract the effects of distance with XR technologies. In this article, we describe and evaluate the Big Head technique, in which a human’s head in VR/AR is scaled up relative to their distance from the observer as a mechanism for enhancing the visibility of non-verbal facial cues, such as facial expressions or eye gaze. To better understand and explore this technique, we present two complimentary human-subject experiments in this article. In our first experiment, we conducted a VR study with a head-mounted display to understand the impact of increased or decreased head scales on participants’ ability to perceive facial expressions as well as their sense of comfort and feeling of “uncannniness” over distances of up to 10 m. We explored two different scaling methods and compared perceptual thresholds and user preferences. Our second experiment was performed in an outdoor AR environment with an optical see-through head-mounted display. Participants were asked to estimate facial expressions and eye gaze, and identify a virtual human over large distances of 30, 60, and 90 m. In both experiments, our results show significant differences in minimum, maximum, and ideal head scales for different distances and tasks related to perceiving faces, facial expressions, and eye gaze, and we also found that participants were more comfortable with slightly bigger heads at larger distances. We discuss our findings with respect to the technologies used, and we discuss implications and guidelines for practical applications that aim to leverage XR-enhanced facial cues.

The visibility of an image semi-transparently overlaid on another image varies significantly, depending on the content of the images. This makes it difficult to maintain the desired visibility level when the image content changes. To tackle this problem, we developed a perceptual model to predict the visibility of the blended results of arbitrarily combined images. Conventional visibility models cannot reflect the dependence of the suprathreshold visibility of the blended images on the appearance of the pre-blended image content. Therefore, we have proposed a visibility model with a content-adaptive feature aggregation mechanism, which integrates the visibility for each image feature (i.e., such as spatial frequency and colors) after applying weights that are adaptively determined according to the appearance of the input image. We conducted a large-scale psychophysical experiment to develop the visibility predictor model. Ablation studies revealed the importance of the adaptive weighting mechanism in accurately predicting the visibility of blended images. We have also proposed a technique for optimizing the image opacity such that users can set the visibility of the target image to an arbitrary level. Our evaluation revealed that the proposed perceptually optimized image blending was effective under practical conditions.