The Role of Tactile Flow in Processing Dynamic Haptic Stimuli

Dynamic stimuli in visual and tactile sensory modalities share fundamental psychophysical features that can be explained by similar computational models. In vision, information about relative motion between objects and the observer are mainly processed by optic flow, which is a 2D field of velocities associated with variation of brightness patterns in the image plane. It provides important information about cues for region and boundary segmentation, shape recovery, and so on. For instance, radial patterns of optic flow are often used to estimate time before contact with an approaching object. We put forward the hypothesis that a similar behavior can be present in the tactile domain, in which an analogous paradigm to optic flow might exist. Moreover, as optic flow is also invoked to explain several visual illusions, including the well-known ”barber-pole” effect and Ouchi’s illusion, we investigate whether similar misperceptions can be observed in the tactile domain as well. After introducing a computational model of tactile flow, which is intimately related to existing models for the visual counterpart a set of experiments aiming at reproducing the corresponding visual illusion in the tactile domain was arranged and performed. Findings of the experiments here reported indicate that visual and tactile flow share similarities at the psychophysical and computational level and may be intended for similar perceptive goals. Results of this analysis can have great impact on engineering side to implement better haptic and multimodal interfaces for human-computer interaction.