Tactile Sensitivity to the Frequency Spectrum of Complex Vibrotactile Signals

Haptic interactions with objects induce complex vibrotactile signals that are central to tactile perception. Despite the broad literature on vibrotactile perception, there is surprisingly little knowledge of the sensory processing of complex tactile signals made of multiple frequencies. To fill this gap, the study reported here investigated the impact of the constitutive pure tones of a complex vibrotactile signal on its perception. Participants completed a 3-AFC task, in which they were asked to identify an odd signal among two complex references. The odd signal was created by removing one pure tone from the reference, which varied in spectral composition, harmonicity, and inter-frequency intervals. Each reference signal was made of either two, three, or four pure tones. The results revealed that the removed pure tone’s value as well as the inter-frequency interval play a significant role on participants’ performance whereas changes in harmonicity, complexity have little impact. In addition, the results showed that the smaller the ratio between the removed frequency and the lowest one of the reference signals, the better the participants’ capacity to identify the one with a missing tone. Overall, the detection of a missing tone in a complex signal predominantly depends on the tone’s frequency value of the removed signal suggesting a tactile sensitivity to the frequency spectrum of complex vibrotactile signals. NEW & NOTEWORTHY This research reports an investigation of the respective roles of frequency range, harmonicity, and complexity on human perception of vibrotactile signals. The results revealed that only pure tones that are close to the lower end of the frequency spectrum are noticed when they are missing. This finding sheds new light on the mechanisms of frequency selectivity in touch. ### Competing Interest Statement The authors have declared no competing interest.