The context of experienced sensory discrepancies shapes multisensory integration and recalibration differently

Abstract

Whether two sensory cues interact during perceptual judgments depends on their immediate properties, but as suggested by Bayesian models, also on the observers a priori belief that these originate from a common source. While in many experiments this a priori belief is considered fixed, in real life it must adapt to the momentary context or environment. To understand the adaptive nature of human multisensory perception we investigated the context-sensitivity of spatial judgements in a ventriloquism paradigm. We exposed observers to audio-visual stimuli whose discrepancy either varied over a wider ({+/-} 46{degrees}) or a narrower range ({+/-} 26{degrees}) and hypothesized that exposure to a wider range of discrepancies would facilitate multisensory binding by increasing participants a priori belief about a common source for a given discrepancy. Our data support this hypothesis by revealing an enhanced integration (ventriloquism) bias in the wider context, which was echoed in Bayesian causal inference models fit to participants data, which assigned a stronger a priori integration tendency during the wider context. Interestingly, the immediate ventriloquism aftereffect, a multisensory response bias obtained following a multisensory test trial, was not affected by the contextual manipulation, although participants confidence in their spatial judgments differed between contexts for both integration and recalibration trials. These results highlight the context-sensitivity of multisensory binding and suggest that the immediate ventriloquism aftereffect is not a purely sensory-level consequence of the multisensory integration process.