Temporal sensitivity and perceived timing in unimodal and crossmodal isochronous sequences.

Temporal judgments depend on sequence regularity and on the sensory modality in which events occur. We asked whether modality-specific sequence history and across-trial modality context make distinct contributions to temporal sensitivity and perceived timing in isochrony judgments. Participants judged whether the sixth event in a six-item sequence occurred earlier or later than expected. The first five events were auditory or visual; the final event either matched this modality or switched modality. The four sequence types were presented either in separate blocks or randomly interleaved across trials; this manipulation is referred to as presentation mode. Temporal sensitivity, indexed by the just noticeable difference (JND), was better for auditory than for visual sequences and better for modality-consistent than for modality-inconsistent sequences. Effects involving presentation mode were treated as descriptive because this factor was between participants and confounded with hardware settings. Perceived timing, indexed by the point of subjective equality (PSE), showed large shifts for modality-switch endings in the interleaved group. The results support a dissociation between sequence-related effects on temporal sensitivity and context-dependent biases in perceived timing.