Ventriloquist Illusion Produced With Virtual Acoustic Spatial Cues and Asynchronous Audiovisual Stimuli in Both Young and Older Individuals.

Marnix Stawicki,Piotr Majdak,Deniz Başkent

doi:10.1163/22134808-20191430

Abstract

Ventriloquist illusion, the change in perceived location of an auditory stimulus when a synchronously presented but spatially discordant visual stimulus is added, has been previously shown in young healthy populations to be a robust paradigm that mainly relies on automatic processes. Here, we propose ventriloquist illusion as a potential simple test to assess audiovisual (AV) integration in young and older individuals. We used a modified version of the illusion paradigm that was adaptive, nearly bias-free, relied on binaural stimulus representation using generic head-related transfer functions (HRTFs) instead of multiple loudspeakers, and tested with synchronous and asynchronous presentation of AV stimuli (both tone and speech). The minimum audible angle (MAA), the smallest perceptible difference in angle between two sound sources, was compared with or without the visual stimuli in young and older adults with no or minimal sensory deficits. The illusion effect, measured by means of MAAs implemented with HRTFs, was observed with both synchronous and asynchronous visual stimulus, but only with tone and not speech stimulus. The patterns were similar between young and older individuals, indicating the versatility of the modified ventriloquist illusion paradigm.

Highlights

In daily life, perception often relies on integration of signals from multiple senses (Beauchamp, 2005; de Gelder and Bertelson, 2003; Ernst and Bülthoff, 2004; Lovelace et al, 2003; Stein and Meredith, 1993, and for a more recent review, Chen and Vroomen, 2013)
A threshold is denoted by the corresponding horizontal dotted line, and the minimum audible angle (MAA) is the difference between the two thresholds
A two-way mixedmodel ANOVA was conducted with the between-subject factor of group and the within-subject factor of AV condition (NoV, SyncV, and asynchronous visual stimulus (AsyncV))

Summary

Introduction

Perception often relies on integration of signals from multiple senses (see Note 1) (Beauchamp, 2005; de Gelder and Bertelson, 2003; Ernst and Bülthoff, 2004; Lovelace et al, 2003; Stein and Meredith, 1993, and for a more recent review, Chen and Vroomen, 2013). The ventriloquism effect has often been quantified using the spatial ventriloquist paradigm, in which the location of the perceived event for synchronously presented but spatially separated auditory and visual stimuli is reported, and compared to the location of the auditory stimulus presented alone (Bermant and Welch, 1976; Bertelson and Aschersleben, 1998) In this paradigm, the perceived target auditory position is pulled towards the visual stimulus (Pick et al, 1969) and a larger lateral displacement in reporting location is required for a correct judgment. When quantifying the amount of audiovisual (AV) interaction in terms of the size of the ventriloquism effect, we essentially could make use of the magnitude of the MAA

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Conclusion