Haptically Induced Illusory Self-motion and the Influence of Context of Motion

The ability of haptic stimuli to augment visually and auditorily induced self-motion illusions has in part been investigated. However, haptically induced illusory self-motion in environments deprived of explicit motion cues remain unexplored. In this paper we present an experiment performed with the intention of investigating how different virtual environments – contexts of motion – influences self-motion illusions induced through haptic stimulation of the feet. A concurrent goal was to determine whether horizontal self-motion illusions can be induced through stimulation of the supporting areas of the feet. The experiment was based on the a within-subjects design and included four conditions, each representing one context of motion: an elevator, a train compartment, a bathroom, and a completely dark environment. The audiohaptic stimuli was identical across all conditions. The participants’ sensation of movement was assessed by means of existing measures of illusory self-motion, namely, reported self-motion illusion per stimulus type, illusion compellingness, intensity and onset time. Finally the participants were also asked to estimate the experienced direction of movement. While the data obtained from all measures did not yield significant differences, the experiment did provide interesting indications. If motion is simulated through implicit motion cues, then the perceived context does influence the magnitude of displacement and the direction of movement of self-motion illusions as well as whether the illusion is experienced in the first place. Finally, the experiment confirmed that haptically induced illusory self-motion in the horizontal plane is indeed possible.