Detection of linear temporal drift in sound sequences: empirical data and modelling principles

Three experiments determined the perceptual threshold (JND) for detecting tempo change; i.e. linear continuous increase or decrease in inter onset interval (IOI) in sequences with 2-9 brief sounds. JND decreased as a power function of the number of intervals presented (Expt. 1). JND increased with IOI and exhibited breakpoints in this respect close to 1 and 1.4 s (Expt. 3), in agreement with previous results for serial interval production. No interaction was apparent between IOI and number of intervals (Expt. 2). None of the experiments showed any effect of direction (increasing or decreasing intervals). The results are inconsistent with several conceivable principles for perceiving tempo change, except for one in which the external intervals are compared with the intervals generated by an internal, periodic process. The plausibility of this principle is discussed in the light of recent research on sensorimotor synchronisation.