Evidence for the Common Coding of Location in Auditory and Visual Space

Abstract

Perception of space is a multimodal construct and orienting our eyes towards a light, sound or touch occurs effortlessly, despite coordinate transformations that have to occur from head-based (sounds) or body-centred (touch) coordinates to eye-centred coordinates. One possible explanation for this effortless orientation behaviour is that space is coded on a common, supramodal map utilised in maintaining locations. Here we present two experiments in support of the view that space is coded on such a common map. The first experiment shows that both, auditory and visual space show similar illusory distortions induced by saccades. Sixteen subjects were asked to judge the direction of an apparent motion straddling a saccade, revealing shifts in judging the direction of auditory as well as visual stimuli in direction of the saccade. Furthermore, the effects were correlated across modalities: Individuals with a large effect in one modality also revealed a large effect in the other modality. This finding suggests that eye movements affect perception of position regardless of the modality in which it is presented. Further evidence comes from the flash-grab effect, the illusory position shift of a brief transient presented on a moving object. We asked observers to judge the location of a transient presented on a moving target in the auditory or visual modality. In both cases, observers reported the location to be further in direction of the motion, suggesting that this position extrapolation is modality invariant. Together the results of these experiments suggest a common mechanism underlying the perception of space across modalities.

Meeting abstract presented at VSS 2015