Multisensory cutaneous displays have been developed to enhance the realism of objects touched in virtual environments. However, when stimuli are presented concurrently, tactile stimuli can mask thermal perception and so both these modalities may not be available to convey information to the user. In this study, we aim to determine the simultaneity window using the Simultaneity Judgment Task. A device was created that could present both tactile and thermal stimuli to the thenar eminence of the participant’s left hand with various stimulus onset asynchronies (SOA). The experimental results indicated that the simultaneity window width was 639 ms ranging from -561 ms to 78 ms. The point of subjective simultaneity (PSS) was at -242 ms, indicating that participants perceived simultaneity best when the thermal stimulus preceded the tactile stimulus by 242 ms. These findings have implications for the design of stimulus presentation in multisensory cutaneous displays.
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Haptic and Audio Interaction Design
There are fundamental differences between the tactile and thermal sensory systems that must be accommodated when designing multisensory cutaneous displays for use in virtual or teleoperated robotic environments. In this review we highlight the marked temporal and spatial differences between the senses of cold and warmth as revealed in psychophysical experiments. Cold and warmth are distinct senses with marked differences in the time taken to respond to stimulation and in their temporal filtering processes. Such variations must be taken into account when time-varying profiles of thermal stimulation are delivered to the skin concurrent with tactile stimulation since the resulting sensations will not be perceived on the same time scale. Although it is often reported that the thermal senses are markedly inferior to the sense of touch with respect to their spatial acuity, it is also clear that there is considerable variability across the body in the accuracy with which thermal stimuli can be localized. The distal to proximal gradient in thermal acuity suggests that locations other than the palmar surface of the hand are better suited for displaying thermal cues, in contrast to the situation for tactile inputs. As was noted for temporal processes, there are differences between localizing warmth and cold stimuli, with localization being superior for cold. These properties provide benchmarks that can be used in designing thermal and multisensory displays.
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- Award ID(s):
- 2006152
- NSF-PAR ID:
- 10353847
- Editor(s):
- Saitis, C.; Farkhatdinov, I; Papetti, S.
- Date Published:
- Journal Name:
- Haptic and Audio Interaction Design
- Volume:
- LNCS 13417
- Page Range / eLocation ID:
- 48-58
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Graphical representations are ubiquitous in the learning and teaching of science, technology, engineering, and mathematics (STEM). However, these materials are often not accessible to the over 547,000 students in the United States with blindness and significant visual impairment, creating barriers to pursuing STEM educational and career pathways. Furthermore, even when such materials are made available to visually impaired students, access is likely through literalized modes (e.g., braille, verbal description), which is problematic as these approaches (1) do not directly convey spatial information and (2) are different from the graphic-based materials used by students without visual impairment. The purpose of this study was to design and evaluate a universally accessible system for communicating graphical representations in STEM classes. By combining a multisensory vibro-audio interface and an app running on consumer mobile hardware, the system is meant to work equally well for all students, irrespective of their visual status. We report the design of the experimental system and the results of an experiment where we compared learning performance with the system to traditional (visual or tactile) diagrams for sighted participants (
n = 20) and visually impaired participants (n = 9) respectively. While the experimental multimodal diagrammatic system (MDS) did result in significant learning gains for both groups of participants, the results also revealed no statistically significant differences in the capacity for learning from graphical information across both comparison groups. Likewise, there were no statistically significant differences in the capacity for learning from graphical information between the stimuli presented through the experimental system and the traditional (visual or tactile) diagram control conditions, across either participant group. These findings suggest that both groups were able to learn graphical information from the experimental system as well as traditional diagram presentation materials. This learning modality was supported without the need for conversion of the diagrams to make them accessible for participants who required tactile materials. The system also provided additional multisensory information for sighted participants to interpret and answer questions about the diagrams. Findings are interpreted in terms of new universal design principles for producing multisensory graphical representations that would be accessible to all learners. -
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Abstract Individual differences in tactile acuity have been correlated with age, gender and finger size, whereas the role of the skin's stiffness has been underexplored. Using an approach to image the 3‐D deformation of the skin surface during contact with transparent elastic objects, we evaluate a cohort of 40 young participants, who present a diverse range of finger size, skin stiffness and fingerprint ridge breadth. The results indicate that skin stiffness generally correlates with finger size, although individuals with relatively softer skin can better discriminate compliant objects. Analysis of contact at the skin surface reveals that softer skin generates more prominent patterns of deformation, in particular greater rates of change in contact area, which correlate with higher rates of perceptual discrimination of compliance, regardless of finger size. Moreover, upon applying hyaluronic acid to soften individuals’ skin, we observe immediate, marked and systematic changes in skin deformation and consequent improvements in perceptual acuity in differentiating compliance. Together, the combination of 3‐D imaging of the skin surface, biomechanics measurements, multivariate regression and clustering, and psychophysical experiments show that subtle distinctions in skin stiffness modulate the mechanical signalling of touch and shape individual differences in perceptual acuity.
Key points Although declines in tactile acuity with ageing are a function of multiple factors, for younger people, the current working hypothesis has been that smaller fingers are better at informing perceptual discrimination because of a higher density of neural afferents.
To decouple relative impacts on tactile acuity of skin properties of finger size, skin stiffness, and fingerprint ridge breadth, we combined 3‐D imaging of skin surface deformation, biomechanical measurements, multivariate regression and clustering, and psychophysics.
The results indicate that skin stiffness generally correlates with finger size, although it more robustly correlates with and predicts an individual's perceptual acuity.
In particular, more elastic skin generates higher rates of deformation, which correlate with perceptual discrimination, shown most dramatically by softening each participant's skin with hyaluronic acid.
In refining the current working hypothesis, we show the skin's stiffness strongly shapes the signalling of touch and modulates individual differences in perceptual acuity.
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Recent advances in extended reality (XR) technologies make seeing and hearing virtual objects commonplace, yet strategies for synthesizing haptic interactions with virtual objects continue to be limited. Two design principles govern the rendering of believable and intuitive haptic feedback: movement through open space must feel “free” while contact with virtual objects must feel stiff. Herein, a novel multisensory approach that conveys proprioception and effort through illusory visual feedback and refers to the wrist, via a bracelet interface, discrete and continuous interaction forces that would otherwise occur at the hands and fingertips, is presented. Results demonstrate that users reliably discriminate the stiffness of virtual buttons when provided with multisensory pseudohaptic feedback, comprising tactile pseudohaptic feedback (discrete vibrotactile feedback and continuous squeeze cues in a bracelet interface) and visual pseudohaptic illusions of touch interactions. Compared to the use of tactile or visual pseudohaptic feedback alone, multisensory pseudohaptic feedback expands the range of physical stiffnesses that are intuitively associated with the rendered virtual interactions and reduces individual differences in physical‐to‐virtual stiffness mappings. This multisensory approach, which leaves users' hands unencumbered, provides a flexible framework for synthesizing a wide array of touch‐enabled interactions in XR, with great potential for enhancing user experiences.
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Current wearable haptic display technology is limited by the lack of broadband tactors capable of delivering rich haptic effects across the entire perceptible frequency range. Audio speakers are often used in laboratory studies as broadband tactors, but it is difficult to attach them to skin and maintain contact during movement. Commercially-available narrowband tactors are small, low in cost and power efficient. We investigate the idea of interleaving narrowband tactile stimuli to achieve broadband effects. Twelve participants performed pairwise discrimination of two stimulus alternatives using two broadband tactors. One alternative was a broadband vibration composed of the sum of a mid- and a high-frequency vibration, delivered by a single tactor. The other alternative consisted of the mid-frequency component delivered by one tactor and the high-frequency by the other. The upper arm was chosen for stimulation because the tactors can be placed within the two-point limen of the skin. The sensitivity index results were significantly below 1.0, the criterion for discrimination threshold, thereby confirming that broadband haptic effects can be achieved by placing narrowband tactors with mid and high resonant frequencies within the skin’s spatial resolution. We provide guidelines and examples of applying our findings to the design of wearable haptic displays.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1007/978-3-031-15019-7_5
