Effect of Subthreshold Electrotactile Stimulation on the Perception of Electrovibration

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 the Likert 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.