Effect of stimulus onset and offset asynchrony on audiovisual temporal recalibration.

When short audiovisual stimuli are presented with a consistent temporal lag, adaptive temporal recalibration occurs to reduce the asynchrony between the stimuli. We investigated adaptive temporal recalibration in prolonged audiovisual stimuli. Specifically, we examined whether temporal recalibration occurs for both the onset and offset of stimuli when these stimulus parts can be distinguished. We also examined whether a constant temporal lag (the auditory stimulus preceded or followed the visual stimulus by 240 ms or 0 ms) at the onset (or offset) of the audiovisual stimuli would allow recalibration for the stimuli's offset (or onset). Experiments 1 and 2 explored whether temporal recalibration occurs at the audiovisual stimuli's onset (or offset) when the onset (or offset) is asynchronous in the adaptation phase. Significant temporal recalibration was found only in the auditory leading condition in these experiments. Experiments 3 and 4 investigated whether temporal recalibration occurs at the audiovisual stimuli's offset (or onset) when the onset (or offset) was asynchronous in the adaptation phase. No significant temporal recalibration was observed in auditory and visual leading conditions in these experiments. These results demonstrated that temporal asynchrony adaptation is only effective when the temporal context (onset or offset) of adapting and test events is matched. The present results suggest that the adaptive temporal recalibration process for prolonged audiovisual stimuli depends upon the onset/offset channel processes and awareness of the temporal lag between those stimulus parts, rather than upon some automatic processing of each stimulus part.