Abstract
Perception in multi-sensory environments involves both grouping and segregation of events across sensory modalities. Temporal coincidence between events is considered a strong cue to resolve multisensory perception. However, differences in physical transmission and neural processing times amongst modalities complicate this picture. This is illustrated by cross-modal recalibration, whereby adaptation to audio-visual asynchrony produces shifts in perceived simultaneity. Here, we examined whether voluntary actions might serve as a temporal anchor to cross-modal recalibration in time. Participants were tested on an audio-visual simultaneity judgment task after an adaptation phase where they had to synchronize voluntary actions with audio-visual pairs presented at a fixed asynchrony (vision leading or vision lagging). Our analysis focused on the magnitude of cross-modal recalibration to the adapted audio-visual asynchrony as a function of the nature of the actions during adaptation, putatively fostering cross-modal grouping or, segregation. We found larger temporal adjustments when actions promoted grouping than segregation of sensory events. However, a control experiment suggested that additional factors, such as attention to planning/execution of actions, could have an impact on recalibration effects. Contrary to the view that cross-modal temporal organization is mainly driven by external factors related to the stimulus or environment, our findings add supporting evidence for the idea that perceptual adjustments strongly depend on the observer's inner states induced by motor and cognitive demands.
Highlights
Perception requires actively processing multiple sources of information arriving to the brain from various sensory modalities
It is interesting to investigate pre-test values across the conditions to control for potential baseline differences in perception of subjective simultaneity (PSS) or standard deviation (SD) between the experimental groups assigned to different action types, previous to any adaptation
To further investigate this trend, a Games-Howell post-hoc test [non-parametric was used because lack of homocedasticity; Levene’s test F(2, 45) = 3.197, p = 0.05] revealed that the SD in the grouping condition (98 ± 45 ms, values corresponding to the mean ± standard deviation) was larger than in the control condition (66 ± 21 ms, p = 0.044, Cohen’s ds = 0.91, Hedges’s g s = 0.89), but was not different from the segregation condition (87 ± 45 ms, p = 0.769, Cohen’s ds = 0.24, Hedges’s g s = 0.24)
Summary
Perception requires actively processing multiple sources of information arriving to the brain from various sensory modalities. Temporal coincidence amongst inputs in different modalities is generally claimed to play a paramount role in guiding the organization of events into multisensory objects (Meredith et al, 1987). At the time information is available via different sensory modalities, the original temporal relations of the events at source are not preserved. This is due to differences in transmission velocities between different sorts of physical energies as well as different transduction and neural processing times between sensory pathways (e.g., King, 2005). It is well known that the subjective experience of cross-modal synchrony is influenced both by external and cognitive factors other
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