Action-contingent vibrotactile flow facilitates the detection of ground level obstacles with a partly virtual sensory substitution device

This research considers a sensory substitution device that allows the exploration of the environment through normal walking, leaning and standing. The device includes an array of 24 coin motors placed vertically on the torso, with the intensity of vibration of each motor being a function of the distance to the first-encountered object. Thresholds were determined for the detection of ground-level obstacles (raised target platforms). On average, blindfolded participants were able to detect platforms with heights of 9 to 17 cm, but the thresholds differed for different experimental conditions. Experiment 1 showed that the detection threshold is lower for use with exploratory movements than for use without exploratory movements. Experiments 2 and 3 compared dynamic groups, who made exploratory movements and received vibrotactile flow contingent on their movements, with yoked groups, who received the same vibrotactile flow as the dynamic groups independently of their own movements. The detection thresholds were lower for the dynamic groups than for the yoked groups, meaning that the contingency of vibrotactile flow on exploratory movements is important beyond a higher-order vibrotactile flow by itself.