Bi-directional audiovisual influences on temporal modulation discrimination.

Cross-modal interactions of auditory and visual temporal modulation were examined in a game-like experimental framework. Participants observed an audiovisual stimulus (an animated, sound-emitting fish) whose sound intensity and/or visual size oscillated sinusoidally at either 6 or 7 Hz. Participants made speeded judgments about the modulation rate in either the auditory or visual modality while doing their best to ignore information from the other modality. Modulation rate in the task-irrelevant modality matched the modulation rate in the task-relevant modality (congruent conditions), was at the other rate (incongruent conditions), or had no modulation (unmodulated conditions). Both performance accuracy and parameter estimates from drift-diffusion decision modeling indicated that (1) the presence of temporal modulation in both modalities, regardless of whether modulations were matched or mismatched in rate, resulted in audiovisual interactions; (2) congruence in audiovisual temporal modulation resulted in more reliable information processing; and (3) the effects of congruence appeared to be stronger when judging visual modulation rates (i.e., audition influencing vision), than when judging auditory modulation rates (i.e., vision influencing audition). The results demonstrate that audiovisual interactions from temporal modulations are bi-directional in nature, but with potential asymmetries in the size of the effect in each direction.