The effects of space on Multisensory Integration.

Abstract

The integration of sensory signals from different modalities is sensitive not only to the spatial and temporal relationship of these sensory signals, but also to their intensity. It is said that low intensity unimodal stimuli elicit a larger integration response when presented together than high intensity unimodal stimuli do. This phenomenon is also known as inverse effectiveness. Although the mechanics of inverse effectiveness in two-dimensional space are well established, for three- dimensional space this is not so much the case. In the present study, stimuli of different intensities were presented in near and far space in order to elicit an inverse effectiveness effect. This way a possible interaction between depth and inverse effectiveness could be examined. Integration was present in both near and far space, and stimuli of high and low intensity behaved according to the inverse effectiveness rule in both near and far space. Although the difference in integration between high and low intensity stimuli did not differ between near and far space, an interaction effect of space with inverse effectiveness was found when comparing the near space high intensity condition with the far space low intensity condition. This outcome, together with a marginally significant main effect of distance on integration, led us to the conclusion that space on its own is too weak of a factor to significantly influence integration, but in conjunction with inverse effectiveness has an effect on multisensory integration.