Abstract:
Effects of deviations from temporal expectations on tempo discrimination were examined using eight-tone isochronous sequences with a fixed inter-onset-interval (IOI) of 400 ms. On each trial, the eight-tone standard sequence was followed by a two-tone comparison sequence with an IOI that was shorter, longer, or the same as that of the standard. Temporal deviations were introduced by advancing or delaying the onset of the comparison sequence relative to the ``expected'' onset time, defined as an extension of the periodicity of the standard (800 ms after the onset of the last tone) and reinforced on every trial in the first trial block. Discrimination thresholds and points of subjective equality were determined for early, late, and expected onsets under mixed and blocked presentation of the onset conditions. Under mixed presentation, early onsets produced more ``shorter'' judgments and late onsets produced more ``longer'' judgments. Timing also affected sensitivity, with lower thresholds for tempo increases in the early-onset conditions and lower thresholds for tempo decreases in the late-onset conditions. No such systematic shifts in bias and threshold were observed with the reduced temporal uncertainty of blocked presentation. Implications for interval- and entrainment-based models of time perception are discussed. [Work supported by a UQ postdoctoral fellowship and NIDCD.]