Discrepancy between impression formation and perception of temporal congruency in audio-visual stimuli

We examined the relation between the perception and impression formation of temporal congruency in audio-visual stimuli. The luminance of the visual stimulus changed repeatedly with a constant temporal frequency. The audio stimulus was periodic drum sounds. In the phase-asynchrony condition, the audio stimulus was varied in its phase. In the frequency-asynchrony condition, it was varied in its temporal frequency. Nine conditions were used for asynchrony between the audio and visual stimuli (0, +/- 48, +/- 96, +/- 192, +/- 384 ms). The results showed that the participants had an impression of the temporal congruency even if they perceived asynchronicity in the audio-visual stimulus. This result was particularly true when the audio-visual stimulus was slow. Both processing that underlies impression formation and processing that underlies the perceptual judgment consider not only the time lag between the audio and the visual stimuli, but also the temporal frequency of the stimuli. These results suggest that the rule underlying the impression formation of the temporal congruency for audio-visual stimuli differs from that underlying the perceptual temporal order judgment for audio-visual stimuli.