Temporal recalibration involves adaptation at two time scales

Abstract

We investigate the time constant of recovery from adaptation to temporal asynchrony. Subjects adapted to a 4-min movie of a nail being hammered, a naturalistic animation with strong audiovisual temporal cues. The movie soundtrack had a constant asynchrony of either ±200 ms. Following adaptation, we sampled synchrony judgments every 2 seconds for 2 min using a brief audiovisual synchrony task (a flash and beep). The flash and beep varied over several ±SOAs and subjects indicated whether they were synchronous. Binning the synchrony responses within a short, rolling time window we obtained estimates of PSS over the course of recovery from temporal adaptation. The rolling average PSS showed a significant recalibration initially followed by a clear recovery function, with PSSs steadily returning to baseline after ∼60 s. We also analysed short-time scale recalibration by testing for adaptation effects between successive synchrony probes. Although these probes were brief (60 ms), we found that a given synchrony judgment in the post adaptation period was strongly influenced by the sign of the previous synchrony probe, showing an adaptation effect in the direction of the preceding synchrony probe’s SOA. In sum, these results show long- and short-scale temporal recalibration effects, with the short-scale inter-probe effects superimposed on the long-scale recalibration. In a second experiment, we delayed the synchrony probes until 60 s post-adaptation and observed no long-scale temporal recalibration, showing there is no storage of long-scale temporal adaptation.