Does an auditory perceptual illusion affect on-line auditory action control? The case of (de)accentuation and synchronization.

Many recent studies have investigated whether visual (spatial) illusions affect visual (spatio-temporal) action control, with results that are far from simple. The present study asks the analogous question with regard to auditory temporal perception and action timing. The auditory illusion chosen for this particular study is the effect of increasing or decreasing the intensity of a tone in a sequence (i.e., accentuation or deaccentuation) on its perceived relative time of occurrence. The motor task is sensorimotor synchronization (finger tapping), specifically the automatic phase correction response to an advanced or delayed tone in a sequence. The strong hypothesis was that (de)accentuation would affect perceptual judgments of the tone's relative time of occurrence, but would have no effect at all on the phase correction response. The results of two experiments, if averaged across participants, confirm these predictions and furthermore suggest that individual perceptual and sensorimotor effects of (de)accentuation are uncorrelated. It is argued that perception and motor control in this case probably rely on different kinds of temporal information: relative versus absolute time of occurrence. Two unexpected findings complicate the results, however: the perceptual illusion was asymmetric, occurring only for delayed tones; and many individual participants did show significant differences in their phase correction response to accented and deaccented tones, although the direction of that difference varied.