Mapping temporal expectancies for different rhytmical surfaces: The role of metric structure and phenomenal accents

This study explores the rules regulating the formation of temporal expectancies when we listen to a rhythmic sequence and extract regularities (or invariant temporal information) projecting them in the near future. Our ability to generate these expectancies is widely dependant on the metric structure suggested by the patterns we entrain to. In Experiment 1, we mapped temporal expectancies evoked by three different repeating patterns in which the phenomenal accents strength was manipulated keeping the metric structure constant in all three patterns. Results of the test tone timing evaluation reveal that expectancy waves are quite short (after the stimulus stops) and very dependent on phenomenal accent strength. In Experiment 2, we used four patterns with different metric structures and lengths: two patterns inducing isochronous meters, and a pattern inducing a Non-Isochronous structure. All the patterns were composed following a rhythm complexity evaluation algorithm. The timing evaluation judgment task after entraining to the patterns was identical to Exp. 1. Results confirm the crucial role of phenomenal accents time position and strength, and show that Isochronous meters generate strong and periodic expectancy waves, while Non-Isochronous meters tend to evoke periodicities of a different level. Our results are consistent with the recent oscillator models of attending. Discussion proposes an interpretation of the results with special attention devoted to the interpretation of N-I meters effects.