Audiovisual temporal order judgments

In two experiments, we examined the extent to which audiovisual temporal order judgments (TOJs) were affected by spatial factors and by the dimension along which TOJs were made. Pairs of auditory and visual stimuli were presented from either the left and/or right of fixation at varying stimulus onset asynchronies (SOAs), and participants made unspeeded TOJs regarding either 'Which modality was presented first?' (experiment 1), or 'Which side was presented first?' (experiment 2). Modality TOJs were more accurate (i.e. just-noticeable differences, JNDs, were smaller) when the auditory and visual stimuli were presented from different spatial positions rather than from the same position, highlighting an important potential confound inherent in previous research. By contrast, spatial TOJs were unaffected by whether or not the two stimuli were presented in different modalities. A between-experiments comparison revealed more accurate performance (i.e. smaller JNDs) when people reported which modality came first than when they reported which side came first for identical bimodal stimulus pairs. These results demonstrate that multisensory TOJs are critically dependent on both the relative spatial position from which stimuli are presented and on the particular dimension being judged.