Some classical studies on temporal order judgments (TOJ) suggested a single central process comparing stimulus onsets across modalities. The prevalent current view suggests that there is modality-specific timing estimation followed by a cross-modal stage. If the latter view is correct, TOJ's may vary depending on stimulus modality. Further, if TOJ is based only on onsets, stimulus duration should be irrelevant. To address these issues, we used both unisensory and multisensory stimuli to test whether unisensory duration processing influences cross-modal TOJ's. The stimuli were auditory noise bursts, visual squares, and their cross-modal combinations presented at 10, 40 and 500 ms durations, and various stimulus onset asynchronies. Psychometric functions were measured with an identical task in all conditions: On each trial, two stimuli were presented, one to the left, the other to the right of fixation. The participants judged which one started first. TOJ's were little affected by stimulus duration, implying that they are mainly determined by stimulus onsets. Throughout, the cross-modal just noticeable differences were larger than the unisensory ones. In accordance with the current view, our results suggest that cross-modal TOJ's require a comparison of timing after modality-specific estimations.
Keywords: Audiovisual; Cross-modal; Duration; Multisensory; Temporal order judgment; Time perception.