Haptic Illusion Research Articles

Avatar Embodiment Enhances Haptic Confidence on the Out-of-Body Touch Illusion.

In the real world, our bodies influence how we perceive ourselves and how others perceive us. Our body can also affect estimations of object sizes and distances. But how does our body affect our haptic experience? Here, we examined the modulation of a visuo-haptic illusion of touch on a virtual stick in virtual reality, when participants were embodied in an avatar and when they were not. During the experiments participants (n = 49) received successions of three taps delivered from two independent controllers while they saw visual stimuli presented sequentially along the virtual stick. The stimulation pattern resulted in a robust illusion of tapping directly on the virtual stick. After each trial, participants were asked to report where they perceived the taps. We found that participants in both the body and no-body conditions displaced the second tap toward the center of the stick, and reported similar levels of certainty about their reported location. However, the illusion of touch on the stick, as measured by the reported location of the tap, was significantly stronger for those who had a virtual body than those who did not. Therefore, our study shows that avatar embodiment can change haptic perception.

1F3-1 Study on Quantitative Evaluation of Haptic Illusion Induced by Visual Stimulus

1F3-1 Study on Quantitative Evaluation of Haptic Illusion Induced by Visual Stimulus

The contradictory influence of velocity: representational momentum in the tactile modality.

Representational momentum (RM) is the term used to describe a systematic mislocalization of dynamic stimuli, a forward shift; that is, an overestimation of the location of a stimulus along its anticipated trajectory. In the present study, we investigate the effect of velocity on tactile RM, because two distinct and contrasting predictions can be made, based on different theoretical accounts. According to classical accounts of RM, based on numerous visual and auditory RM studies, an increase of the forward shift with increasing target velocity is predicted. In contrast, theoretical accounts explaining spatiotemporal tactile illusions such as the tau or cutaneous rabbit effect predict a decrease of the forward shift with increasing target velocity. In three experiments reported here, a tactile experimental setup modeled on existing RM setups was implemented. Participants indicated the last location of a sequence of three tactile stimuli, which either did or did not imply motion in a consistent direction toward the elbow/wrist. Velocity was manipulated by changing the interstimulus interval as well as the duration of the stimuli. The results reveal that increasing target velocity led to a decrease and even a reversal of the forward shift, resulting in a backward shift. This result is consistent with predictions based on the evidence from tactile spatiotemporal illusions. The theoretical implications of these results for RM are discussed. NEW & NOTEWORTHY This study tests two distinct predictions concerning the influence of velocity on the localization of dynamic tactile stimuli. We demonstrate for tactile stimuli that with increasing velocity, a misperception in the direction of anticipated motion (termed "representational momentum") turns into a misperception against the direction of motion. This result is in line with predictions based on tactile spatiotemporal illusions but challenges classical theoretical accounts of representational momentum based on evidence from vision and audition.

Surface Sensations Generated by Tactile Illusion

Surface Sensations Generated by Tactile Illusion

Creating an Illusion of Movement between the Hands Using Mid-Air Touch.

Apparent tactile motion has been shown to occur on many contiguous parts of the body, such as the fingers, forearms, and back. More recently, the illusion has also been elicited on non-contiguous parts of the body, such as between one hand and the other, either when the hands are interconnected or not interconnected by an object (e.g., when holding a tablet or not). Here, we explore the reproducibility of the intermanual tactile illusion of movement between two free hands by employing mid-air tactile stimulation. We investigate the optimal parameters to generate a continuous and smooth motion using two arrays of ultrasound speakers and two stimulation techniques (i.e., static versus dynamic focal point). In the first experiment, we investigate the occurrence of the illusion when using a static focal point, and we define a perceptive model. In the second experiment, we examine the illusion using a dynamic focal point, defining a second perceptive model. Finally, we discuss the differences between the two techniques.

Influence of Size-Weight Illusion on Usability in Haptic Human-Robot Collaboration.

Collaborative power amplifying robots are accepted as one solution to overcome flexibility and ergonomic issues in future work and life scenarios. The handling of various sized and weighted objects in heterogeneous environments pose a particular challenge to the often applied admittance control. Haptic illusions, especially the Size-Weight Illusion (SWI), where the smaller of two equally weighted objects is perceived to be heavier, can have malicious, disturbing, or to some extent useful influence on system stability and usability. A within-subjects experiment was conducted with 40 participants and three within-factors (size, weight, and movement type), to investigate the occurrence and influence of SWI in bimanual fast-imprecise and slow-precise planar manipulation tasks. The illusion was replicated and an influence on usability was found. Further, different control strategies according to object size and mass (static, compensatory, and mismatch) were analyzed and did not show significant effects on task performance. It appears that either no change in assistance or a change according to object size is advisable.

Patients' views on early sensory relearning following nerve repair—a Q-methodology study

Study DesignDescriptive study. IntroductionEarly sensory relearning where the dynamic capacity of the brain is used has been shown to improve sensory outcome after nerve repair. However, no previous studies have examined how patients experience early sensory relearning. Purpose of the StudyTo describe patient’s views on early sensory relearning. MethodsStatements′ scores were analyzed by factor analysis. ResultsThirty-seven consecutive adult patients with median and/or ulnar nerve repair who completed early sensory relearning were included. Three factors were identified, explaining 45% of the variance: (1) “Believe sensory relearning is meaningful, manage to get an illusion of touch and complete the sensory relearning”; (2) “Do not get an illusion of touch easily and need support in their sensory relearning” (3) “Are not motivated, manage to get an illusion of touch but do not complete sensory relearning”. DiscussionMany patients succeed in implementing their sensory relearning. However, a substantial part of the patient population need more support, have difficulties to create illusion of touch, and lack motivation to complete the sensory relearning. To enhance motivation and meaningfulness by relating the training clearly to everyday occupations and to the patient′s life situation is a suggested way to proceed. ConclusionThe three unique factors indicate motivation and sense of meaningfulness as key components which should be taken into consideration in developing programs for person-centered early sensory relearning. Level of Evidence3.

An examination of haptic illusion by disk-rotation

An examination of haptic illusion by disk-rotation

Object Touch by a Humanoid Robot Avatar Induces Haptic Sensation in the Real Hand

Humanoid robot embodiment is a recently developed form of mediated embodiment. In 2 studies, we report and quantify a new haptic (touch) illusion during embodiment of a humanoid robot. Around 60% of the users in our studies reported haptic sensations in their real hand when they observed their robot avatar touching a curtain with its hand. Critically, our study shows for the first time that users can experience haptic sensations from a nonanthropomorphic embodied limb/agent with visual feedback alone (i.e. no haptic feedback provided). The results have important implications for the understanding of the cognitive processes governing mediated embodiment and the design of avatar scenarios.

Design, analysis and experimental validation of an ungrounded haptic interface using a piezoelectric actuator

In this paper, a novel small ungrounded haptic device for spatial guidance is presented. The device uses a piezoelectric actuator to generate the haptic illusion of an external force. Using asymmetric accelerations, the device is thus able to generate a pulling or pushing sensation to a user. A dynamic model of the device is developed, which allows the determination of the optimal parameters to be used. These parameters are the frequency of the input signal and the natural frequency of the device including the connection with the user handle. It is shown that by using a particular input frequency, depending on the natural frequency of the device, the acceleration of the moving mass and its asymmetry are both maximized. Experimental tests show that the device is able to generate a haptic perception in two opposite directions with a success rate ranging from 80% to 86%.

Fishbone Tactile Illusionを利用した触対象の凹知覚の研究(「ハプティックインタラクション」特集)

Fishbone Tactile Illusionを利用した触対象の凹知覚の研究(「ハプティックインタラクション」特集)

Presenting Tactile Illusion at the Toe Pad using Vibration Stimulus on Toenail: Verifying Force Conditions Inducing Tactile Illusion for First Toe

Presenting Tactile Illusion at the Toe Pad using Vibration Stimulus on Toenail: Verifying Force Conditions Inducing Tactile Illusion for First Toe

Fishbone Tactile Illusionを利用した触対象の凹凸知覚(触覚とロボット,2007年度 第2回フォーラム)

Fishbone Tactile Illusionを利用した触対象の凹凸知覚(触覚とロボット,2007年度 第2回フォーラム)

Tactile mouse generating velvet hand illusion on human palm

To enhance virtual reality (VR) generated by tactile displays, we have focused on a novel tactile illusion, called the Velvet Hand Illusion (VHI). In VHI, moving two parallel wires back and forth between the two hands leads humans to perceive a velvet-like surface between their hands. In earlier studies, we revealed that the intensity of VHI could be controlled by a ratio ( r/ D), where r and D are the wire stroke and wire distance, respectively. According to these findings, we investigate in this study whether a common tactile display is able to produce VHI, and whether the ratio can also control VHI intensity. We prepare a dot-matrix display as a tactile display in which moving one line of the display’s pins is considered as a wire pattern. We investigate the VHI intensity with regard to changing the stroke r and the line distance D using paired comparison. Experimental results show that the VHI intensity is increased or decreased by changing r and D. We conclude that VHI can be created by the tactile display, and the intensity of VHI is controlled by changing the ratio of r/ D.

VibrotactileComplianceFeedback for TangentialForceInteraction.

This paper presents a method to generate a haptic illusion of compliance using a vibrotactile actuator when a tangential force is applied to a rigid surface. The novel method builds on a conceptual compliance model where a physical object moves on a textured surface in response to a tangential force. The method plays vibration patterns simulating friction-induced vibrations as an applied tangential force changes. We built a prototype consisting of a two-dimensional tangential force sensor and a surface transducer to test the effectiveness of the model. Participants in user experiments with the prototype perceived the rigid surface of the prototype as a moving, rubber-like plate. The main findings of the experiments are: 1) the perceived stiffness of a simulated material can be controlled by controlling the force-playback transfer function, 2) its perceptual properties such as softness and pleasantness can be controlled by changing friction grain parameters, and 3) the use of the vibrotactile compliance feedback reduces participants' workload including physical demand and frustration while performing a force repetition task.

ラバーハンドイリュージョンにおける力覚・触覚フィードバックの影響に関する研究

Multi-sensory illusion in rubber hand illusion is a well known haptic illusion in the literature. In this study, we introduce Multi-sensory illusion into a form of master slave system to realize a further operability. As a preliminary test, we developed a 1 DOF bilateral rubber hand master slave system and investigated the effect of force feedback on Multi-sensory illusion.

Rich Pinch: Perception of Object Movement with Tactile Illusion.

Vibrotactile feedback is an effective and economical approach for enriching interactive feedback. However, its effects are mostly limited to providing supplementary alarms or conveying the sense of simple object presence or contact. In this paper, we propose a novel tactile feedback method, called Rich Pinch, based on the "out of body" tactile illusion for selecting and manipulating a virtual object using a two-finger pinch gesture. Rich Pinch uses vibration motors attached only to the two fingertips, but can induce illusory feedback, such as tactile touch/contact and directional movement, as felt from the space between the fingers. We first experimentally verify that the "out of body" illusion technique does in fact exist when applied between the fingertips. Then, we compare three different tactile rendering functions to illustrate different resulting perceptual scales and argue to use the tangent-based interpolation in its actual application for a better user performance and experience due to its near-linear perceptual response. Finally, we assess the user experience (focusing on the perception of the object movement of the selected object) of the proposed pinch method by comparing it to the conventional contact-based method. Our results indicate that, with Rich Pinch, users were able to perceive rich dynamic feedback, and clearly preferred it over the conventional method.

Pseudo-haptic feedback in medical teleoperation

Abstract Pseudo-haptic feedback is a haptic illusion based on a mismatch of haptic and visual perception. It is well known from applications in virtual environments. In this work, we discuss the usabiliy of the principle of pseudo-haptic feedback for teleoperation. Using pseudo-haptic feedback can ease the design of haptic medical tele-operation systems. Thereby a user’s grasping force at an isometric user interface is used to control the closing angle of an end effector of a surgical robot. To provide a realistic haptic feedback, the coupling characteristic of grasping force and end effector closing angle is changed depending on acting end effector interaction forces. With an experiment, we show the usability of pseudo-haptic feedback for discriminating compliances, comparable to the mechanical characteristic of muscles relaxed and contracted. The provided results base upon the data of 10 subjects, and 300 trails.

Pile Surface Tactile Simulation: Role of the Slider Shape, Texture Close to Fingerprints, and the Joint Stiffness

Stimulating the human hand with a tactile device in order to simulate pile fabric touch is a challenge. The stimulation has to be designed from the friction characteristics of the investigated pile surfaces, i.e. velvet fabrics. The tactile illusion of pile is given when touching the smooth plate of the tactile stimulator STIMTAC by modulating the coefficient of friction between the plate and the finger during an active movement. In a preliminary study, five tribological features as velvet fabric characteristics were identified, used for the design of the stimulator’s control signal, and validated via psychophysical studies where real and simulated fabrics were compared. But a specific tribological feature described and expected by individuals was missing. Then, a tribological investigation has been done in order to obtain this tribological feature, with the five previous ones, by changing experimental conditions: slider shape, texture, and joint stiffness. The obtained results show that a rounded shape of the slider has an influence only on the friction force level, but a texture of the slider close to fingerprints and a joint stiffness is crucial to obtain the missing characteristic and therefore for the pile surface tribological characterization. The role of the fingerprints in touching grooved surfaces has been published before but not for pile surfaces.

A predictive nature for tactile awareness? Insights from damaged and intact central-nervous-system functioning.

In the present paper, we will attempt to gain hints regarding the nature of tactile awareness in humans. At first, we will review some recent literature showing that an actual tactile experience can emerge in absence of any tactile stimulus (e.g., tactile hallucinations, tactile illusions). According to the current model of tactile awareness, we will subsequently argue that such (false) tactile perceptions are subserved by the same anatomo-functional mechanisms known to underpin actual perception. On these bases, we will discuss the hypothesis that tactile awareness is strongly linked to expected rather than actual stimuli. Indeed, this hypothesis is in line with the notion that the human brain has a strong predictive, rather than reactive, nature.