Although haptic technologies that allow users to touch virtual objects have been actively researched in the academic field of haptics, they are not yet widely adopted in real-world applications. To promote broader adoption, designing haptic stimuli that elicit pleasant sensations is essential since hedonic motivation significantly drives user acceptance. However, how such pleasantness can be effectively induced through haptic stimulation during a user's active exploration remains an open question. Furthermore, it is unclear whether “pseudo-haptics”, a low-cost substitute for physical force feedback, can also serve effectively in this affective context. In this study, we investigated the relationship between the applied force during user actions and the resulting pleasantness, using a bow-dragging and arrow-shooting scenario as a case study. Specifically, we conducted three psychophysical experiments to investigate two types of force feedback. One type was a physical force that stimulated the kinesthetic sense, and the other was a pseudo force induced through visual manipulation. Our results revealed that pleasantness tended to be elicited when physical resistance force was present during bow dragging, whereas this tendency was not observed for pseudo resistance force. While there has been a general assumption that pseudo-haptics can replace physical stimuli to some extent in the rendering of haptic properties, our findings quantitatively show that in our case the two are not interchangeable for eliciting positive affect. We also found that the arrow's flying speed contributed to pleasantness as much as the physical resistance force, suggesting that pleasantness is influenced postdictively. Moreover, across all experiments, perceived pleasantness was strongly correlated with the perceived naturalness of the bow-and-arrow behavior. These findings provide valuable insights for designing pleasant interactions involving continuous force feedback, highlighting the distinct roles of physical and pseudo-haptic cues.

Elastic materials often invite the direct touch of users. It is an open question how seeing elastic materials invokes touch desire. The present study proposes a novel visual feature that modulates apparent elasticity and touch desire. The stimulus for our experiment was a clip in which a computer-rendered elastic surface was indented by a needle-like bar. The features of this stimulus that we focused on were spatial deformation range and indentation depth. Observers rated the following three impressions: apparent elasticity, touch desire, and anticipated touch pleasantness. The results showed that both apparent elasticity and touch desire peaked in the middle of the spatial deformation range. The two impressions also depended on indentation depth and were highly correlated with each other. Anticipated touch pleasantness showed a different peak tendency than the other two. An additional block showed that the deformation realism was not related to the above three impressions. The results suggest that apparent elasticity eliciting touch desire can be determined in the parameter space defined by the spatial deformation range and the indentation depth.

Pseudo-haptics is a method that can provide a haptic sensation without requiring a physical haptic device. The effect of pseudo-haptics is known to depend on the individual, but it is unclear which factors cause individual differences. As the first study establishing a calibration method for these differences in future research, we examined the differences in the pseudo-haptic effect on mouse cursor operation in a desktop environment depending on the age and gender of the user. We conducted an online experiment and collected data from more than 400 participants. The participants performed a task of lifting a virtual object with a mouse pointer. We found that the effect of pseudo-haptics was greater in younger or male participants than in older or female participants. We also found that the effect of pseudo-haptics, which varied with age and gender, can be explained by habituation to the mouse in daily life and the accuracy of detecting the pointer position using vision or proprioception. Specifically, the pseudo-haptic effect was higher for those who used the mouse more frequently and had higher accuracy in identifying the pointer position using proprioception or vision. The results of the present study not only indicate the factors that cause age and gender differences but also provide hints for calibrating these differences.

Feedback on the material properties of a visual object is essential in enhancing the users' perceptual experience of the object when users control the object with touchless inputs. Focusing on the softness perception of the object, we examined how the effective distance of hand movements influenced the degree of the object's softness perceived by users. In the experiments, participants moved their right hand in front of a camera which tracked their hand position. A textured 2D or 3D object on display deformed depending on the participant's hand position. In addition to establishing a ratio of deformation magnitude to the distance of hand movements, we altered the effective distance of hand movement, within which the hand movement could deform the object. Participants rated the strength of perceived softness (Experiments 1 and 2) and other perceptual impressions (Experiment 3). A longer effective distance produced a softer impression of the 2D and 3D objects. The saturation speed of object deformation due to the effective distance was not a critical determinant. The effective distance also modulated other perceptual impressions than softness. The role of the effective distance of hand movements on perceptual impressions of objects under touchless control is discussed.

Advances in haptic technology have led researchers and engineers to seek out killer applications in which users can enjoy an experience of touch in AR/VR spaces. Such applications will respond appropriately to human desire for haptic experiences (i.e., touch desire) and thus it is essential for researchers and engineers to understand the nature of people's touch desires as they arise in the course of daily life. In this study, we employed Twitter data analysis to investigate a diurnal pattern in touch desire. Our results showed that touch desire identified in and extracted from Twitter texts did reveal a diurnal pattern. Touch desire tended to be at its lowest in the morning and increased as the day progressed. The time at which it peaked varied with the specific target of touch desire. Touch desire in relation to other people and objects reached its peak at night, but touch desire in relation to animals reached its peak at noon. These results were confirmed not only by our Twitter text analysis but also by data from other social media and an online survey. In addition, we found that the diurnal pattern of touch desire for each target shows a strong correlation with that of visual desire for the same target. This suggests that the diurnal pattern of touch desire is not limited to the sense of touch but is common to other sensory desires for each target. Our findings suggest that researchers need to take the time of day into account when investigating touch desire. Our findings also offer valuable insights for developers into the design of haptic applications and displays that takes into account the timing of daily peaks in touch desire.

Playing back vibrotactile signals through actuators is commonly used to simulate tactile feelings of virtual textured surfaces. However, there is often a small mismatch between the simulated tactile feelings and intended tactile feelings by tactile designers. Thus, a method of modulating the vibrotactile perception is required. We focus on fine roughness perception and we propose a method using a pseudo-haptic effect to modulate fine roughness perception of vibrotactile texture. Specifically, we visually modify the pointer's position on the screen slightly, which indicates the touch position on textured surfaces. We hypothesized that if users receive vibrational feedback watching the pointer visually oscillating back/forth and left/right, users would believe the vibrotactile surfaces more uneven. We also hypothesized that as the size of visual oscillation is getting larger, the amount of modification of roughness perception of vibrotactile surfaces would be larger. We conducted user studies to test the hypotheses. Results of first user study suggested that users felt vibrotactile texture with our method rougher than they did without our method at a high probability. Results of second user study suggested that users felt different roughness for vibrational texture in response to the size of visual oscillation. These results confirmed our hypotheses and they suggested that our method was effective. Also, the same effect could potentially be applied to the visual movement of virtual hands or fingertips when users are interacting with virtual surfaces using their hands.

We aim to enable additional sensation when using an anthropomorphic finger motion interface. To do so, we applied a conventional method to generate pseduo-haptics. To control the amount of scroll resulting from finger displacement on a display, illusory resistance or pseudo friction was confirmed by subjective evaluation. We first clarified that this illusory resistance influences finger walking behavior such as stride or speed. An additional experiment conducted in public space verified this influence.