Capturing the dynamics of peripersonal space by integrating sound propagation properties and expectancy effects

Abstract

Highlights• Logarithmically distributed auditory distances provides an apt granularity of PPS • Measuring expectation helps to interpret behavioral impact of audiotactile integration • Tactile RTs follows a logarithmic decrease due to audiotactile integration • Peripersonal space is better characterized and quantified with this refinement Abstract BackgroundHumans perceive near space and far space differently. Peripersonal space, i.e. the space directly surrounding the body, is often studied using paradigms based on auditory-tactile integration. In these paradigms, reaction time to a tactile stimulus is measured in the presence of a concurrent auditory looming stimulus. New MethodWe propose here to refine the experimental procedure considering sound propagation properties in order to improve granularity and relevance of auditory-tactile integration measures. We used a logarithmic distribution of distances for this purpose. We also want to disentangle behavioral contributions of the targeted audiotactile integration mechanisms from expectancy effects. To this aim, we added to the protocol a baseline with a fixed sound distance. ResultsExpectation contributed significantly to overall behavioral responses. Subtracting it isolated the audiotactile effect due to the stimulus proximity. This revealed that audiotactile integration effects have to be tested on a logarithmic scale of distances, and that they follow a linear variation on this scale. Comparison with Existing Method(s)The granularity of the current method is more relevant, providing higher spatial resolution in the vicinity of the body. Furthermore, most of the existing methods propose a sigmoid fitting, which rests on the intuitive framework that PPS is an in-or-out zone. Our results suggest that behavioral effects follow a logarithmic decrease, thus a response graduated in space. ConclusionsThe proposed protocol design and method of analysis contribute to refine the experimental investigation of the factors influencing and modifying multisensory integration phenomena in the space surrounding the body.