Tactile input and empathy modulate the perception of ambiguous biological motion

Abstract

Evidence has shown that task-irrelevant auditory cues can bias perceptual decisions regarding directional information associated with biological motion, as indicated in perceptual tasks using point-light walkers (PLWs) (Brooks et al., 2007). In the current study, we extended the investigation of cross-modal influences to the tactile domain by asking how tactile input resolves perceptual ambiguity in visual apparent motion, and how empathy plays a role in this cross-modal interaction. In Experiment 1, we simulated the tactile feedback on the observers' fingertips when the (upright or inverted) PLWs (comprised of either all red or all green dots) were walking (leftwards or rightwards). The temporal periods between tactile events and critical visual events (the PLW's feet hitting the ground) were manipulated so that the tap could lead, synchronize, or lag the visual foot-hitting-ground event. We found that the temporal structures between tactile (feedback) and visual (hitting) events systematically biases the directional perception for upright PLWs, making either leftwards or rightwards more dominant. However, this effect was absent for inverted PLWs. In Experiment 2, we examined how empathy modulates cross-modal capture. Instead of giving tactile feedback on participants' fingertips, we gave taps on their ankles and presented the PLWs with motion directions of approaching (facing toward observer)/receding (facing away from observer) to resemble normal walking postures. With the same temporal structure, we found that individuals with higher empathy were more subject to perceptual bias in the presence of tactile feedback. Taken together, our findings showed that task-irrelevant tactile input can resolve the otherwise ambiguous perception of the direction of biological motion, and this cross-modal bias was mediated by higher level social-cognitive factors, including empathy.

Psychophysics of wearable haptic/tactile perception in a multisensory context

“…In temporal ventriloquism effect, the perceived time onsets/time intervals of target eventsvisual events (with lower temporal resolutions) could usually be biased with the presence of the distractorsauditory stimuli or tactile events (with higher temporal resolutions) when all the events are within the presumed temporal window [14] . By exploiting the temporal ventriloquism effect, we have implemented empirical psychophysical studies to show that the ambiguous percept of visual apparent motion could be resolved with the well-designed (alignments) of auditory inputs [15][16][17][18] and tactile inputs [19,20] . In telepresence, we showed that synchronous perception of cross-modal (visuo-haptic) events was very sensitive to the visual packet loss rate.…”