The Ventriloquist Illusion is Bayes-Optimal
Poster Presentation

Ulrik Beierholm
CNS, Caltech

Steven Quartz
CNS, Caltech

Ladan Shams
Dept. Psychology, UCLA

     Abstract ID Number: 74
     Full text: Not available
     Last modified: July 6, 2005

Abstract
The human nervous system constantly receives input from several senses and has to quickly decide whether and how to integrate the multisensory information.
Dependent on the temporal and spatial congruity between the cues, the visual and auditory cues can either be perceived as originating from one source (integration) or different sources (segregation).
We have previously developed an ideal observer model that through Bayesian inference determines whether and how to integrate or segregate the sensory signals. The model allows complete segregation, complete fusion as well as partial integration. We examined whether this model can explain the ventriloquist illusion which involves spatial perception. The visual stimulus and auditory stimulus were presented at the same or different locations, each at one of five locations. The subject’s task was to indicate the location of the visual stimulus as well as the location of the auditory stimulus in each trial. The subjects’ auditory and visual responses were highly consistent with the ideal observer in all conditions (R2=0.93). This degree of consistency is remarkable considering the fact that the model is predictive, with no free parameters.
We propose that Bayesian inference is a general principle underlying multisensory perception.