Visual and Tactile Contributions to Self-Motion Perception

Oliver Kannape, Psychology, University College Dublin

Abstract
The extent that visual information normally dominates in perception of self-motion through the environment is no better illustrated than by the illusion of self-motion that can be induced by visual field motion (vection). In cases of uncertain visual stimuli however, a multimodal percept can be shifted towards and even ‘captured’ by other senses. We investigated the effects of a foot proprioceptive motion stimulus on performance on a visual motion detection task. The tactile stimulus was created using two specially constructed motion platforms; visual motion was realized using random-dot kinematograms with varying percentages of coherent motion.
2IFC data for the visual motion stimulus were fit by a Bayesian routine for psychometric functions (Kuss, Jäkel, and Wichmann 2005). A significant effect on motion detection thresholds was observed for incongruent foot-visual motion stimuli (t(4)=3.27, p=0.015 < α=0.017) corresponding to the congruency effect. Motion detection thresholds did not profit from combining congruent multimodal stimuli (t(4) = 1.06, p = 0.17).
These results indicate that multisensory facilitation is not evident for spatially separated visual and tactile stimuli as predicted by the spatial rule. More importantly, and against this rule of integration, a significant effect for increasing threshold for incongruent stimuli was seen across all subjects.

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