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Relocating thermal stimuli to the proximal phalanx may not affect vibrotactile sensitivity on the fingertip

Huibert A. J. van Riessen, Yasemin Vardar

TL;DR

This study addresses whether relocating constant thermal stimuli to the proximal phalanx modulates fingertip vibrotactile detection. Using a novel wearable that delivers thermal/pressure cues to the proximal phalanx while presenting a $250$ Hz vibrotactile stimulus to the fingertip, the authors measured detection thresholds across six conditions via a $3$-up/$1$-down staircase in $n=15$ participants and analyzed the data with a Skillings-Mack test. They found no significant cross-modal interference from the relocated thermal cues under fixed pressures, suggesting perceptual independence or adaptive effects for constant stimuli. The findings inform the design of multitouch haptic devices by indicating that relocating thermal feedback away from the fingertip may preserve fingertip vibrotactile sensitivity, with dynamic-stimulation studies proposed for future work.

Abstract

Wearable devices that relocate tactile feedback from fingertips can enable users to interact with their physical world augmented by virtual effects. While studies have shown that relocating same-modality tactile stimuli can influence the one perceived at the fingertip, the interaction of cross-modal tactile stimuli remains unclear. Here, we investigate how thermal cues applied on the index finger's proximal phalanx affect vibrotactile sensitivity at the fingertip of the same finger when employed at varying contact pressures. We designed a novel wearable device that can deliver thermal stimuli at adjustable contact pressures on the proximal phalanx. Utilizing this device, we measured the detection thresholds of fifteen participants for 250 Hz sinusoidal vibration applied on the fingertip while concurrently applying constant cold and warm stimuli at high and low contact pressures to the proximal phalanx. Our results revealed no significant differences in detection thresholds across conditions. These preliminary findings suggest that applying constant thermal stimuli to other skin locations does not affect fingertip vibrotactile sensitivity, possibly due to perceptual adaptation. However, the influence of dynamic multisensory tactile stimuli remains an open question for future research.

Relocating thermal stimuli to the proximal phalanx may not affect vibrotactile sensitivity on the fingertip

TL;DR

This study addresses whether relocating constant thermal stimuli to the proximal phalanx modulates fingertip vibrotactile detection. Using a novel wearable that delivers thermal/pressure cues to the proximal phalanx while presenting a Hz vibrotactile stimulus to the fingertip, the authors measured detection thresholds across six conditions via a -up/-down staircase in participants and analyzed the data with a Skillings-Mack test. They found no significant cross-modal interference from the relocated thermal cues under fixed pressures, suggesting perceptual independence or adaptive effects for constant stimuli. The findings inform the design of multitouch haptic devices by indicating that relocating thermal feedback away from the fingertip may preserve fingertip vibrotactile sensitivity, with dynamic-stimulation studies proposed for future work.

Abstract

Wearable devices that relocate tactile feedback from fingertips can enable users to interact with their physical world augmented by virtual effects. While studies have shown that relocating same-modality tactile stimuli can influence the one perceived at the fingertip, the interaction of cross-modal tactile stimuli remains unclear. Here, we investigate how thermal cues applied on the index finger's proximal phalanx affect vibrotactile sensitivity at the fingertip of the same finger when employed at varying contact pressures. We designed a novel wearable device that can deliver thermal stimuli at adjustable contact pressures on the proximal phalanx. Utilizing this device, we measured the detection thresholds of fifteen participants for 250 Hz sinusoidal vibration applied on the fingertip while concurrently applying constant cold and warm stimuli at high and low contact pressures to the proximal phalanx. Our results revealed no significant differences in detection thresholds across conditions. These preliminary findings suggest that applying constant thermal stimuli to other skin locations does not affect fingertip vibrotactile sensitivity, possibly due to perceptual adaptation. However, the influence of dynamic multisensory tactile stimuli remains an open question for future research.
Paper Structure (8 sections, 5 figures)

This paper contains 8 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Methods
  3. Participants
  4. Experimental setup
  5. Stimuli
  6. Experimental procedure
  7. Results
  8. Discussion

Figures (5)

  • Figure 1: (a) Thermal (blue) stimulus perceived simultaneously by interacting with a material surface at applied contact pressure (red). (b) Relocated thermal (blue) stimulus is applied to the proximal phalanx with a pressure (red) and simultaneously perceived during interaction with the material surface using the fingertip.
  • Figure 2: (a) Experimental setup: 1. custom-designed multi-modal haptic device, 2. data acquisition board, 3. monitor displaying the GUI, 4. variable power supply, 5. Arduino, 6. water pump, 7. armrest, and 8. keyboard. (b) A closer look at the custom-designed haptic device: 1. servo motor, 2. servo motor housing, 3. servo belt, 4. spur gears, 5. force-resisting sensor, 6. NTC thermistor, 7. Peltier element, 8. water-cooling heat sink, 9. moving platform, 10. acrylic mounting plate, 11. force-sensing resistor, and 12. voice-coil actuator
  • Figure 3: Stimuli timing diagram for the vibrotactile sensitivity experiments. A sinusoidal vibrotactile stimulus (250 Hz) with a duration of 1 second was either present in the first or the second interval randomly. Pressure and thermal stimuli were always present during the trial and kept constant throughout all repetitions. The participant had to choose in which of these two intervals the vibrotactile stimulus was present.
  • Figure 4: An example session of the adaptive three-up/one-down staircase method zwislocki2001psychophysical. The threshold value is calculated by averaging the last five reversals at the $\pm$1 dB range. Correct answers are represented by plus signs (+), and minus signs (-) represent incorrect answers. The circles (o) show reversals, and the threshold is indicated with a red line.
  • Figure 5: Boxplots of the vibrotactile detection thresholds. The results corresponding to each experimental condition are color-coded. The center lines show the medians; box limits indicate the 25th and 75th percentiles. The whiskers extend to 1.5 times the interquartile range. Outliers are represented by plus signs (+), and diamonds ($\diamond$) represent sample means. The points (.) show individual threshold values; the sample sizes (n) are indicated under each boxplot.