Detecting perturbations in polyrhythms: Effects of complexity and attentional strategies

Author: Fidali, B. C., Poudrier, Ève, Repp, B. H.
Publication details: Psychological Research 77, 183-195. Published online: 29 December 2011 (DOI 10.1007/s00426-011-0406-8)

Jones et al. in Journal of Experimental Psychology Human Perception and Performance 21:293–307, 1995, showed that a temporal perturbation is easier to detect in a 3:2 polyrhythm than in a single-stream isochronous baseline condition if the two isochronous pulse streams forming the polyrhythm are perceptually integrated: integration creates shorter inter-onset interval (IOI) durations that facilitate perturbation detection. The present study examined whether this beneWt of integration outweighs the potential costs imposed by the greater IOI heterogeneity and memory demands of more complex polyrhythms. In “Experiment 1”, musically trained participants tried to detect perturbations in 3:5, 4:5, 6:5, and 7:5 polyrhythms having one of two divergent pitch separations between pulse streams, as well as in an isochronous base- line condition. “Experiment 2” included an additional 2:5 polyrhythm, additional pitch separations, and instructions to integrate or segregate the two pulse streams. In both experiments, perturbation detection scores for polyrhythms were below baseline, decreased as polyrhythm complexity increased, and tended to be lower at a smaller pitch separation, with little eVect of instructions. Clearly, polyrhythm complexity was the main determinant of detection perfor- mance, which is attributed to the interval heterogeneity and/ or memory demands of the pattern formed by the integrated pulse streams. In this task, perceptual integration was dis- advantageous, but apparently could not be avoided.