Delayed auditory feedback and movement.

It is well known that timing of rhythm production is disrupted by delayed auditory feedback (DAF), and that disruption varies with delay length. We tested the hypothesis that disruption depends on the state of the movement trajectory at the onset of DAF. Participants tapped isochronous rhythms at a rate specified by a metronome while hearing DAF (for piano tones) of differing lengths. Motion capture was used to analyze movement trajectories. Mean Inter-Response Intervals (IRIs) varied as an approximately sinusoidal function of feedback condition, with DAF causing slowed production for shorter delays and speeded production for faster delays. Motion capture analyses revealed that finger velocity at the time of DAF predicted the effect of DAF on mean IRI whereas finger position predicted the variability of IRIs. A second experiment in which participants were instructed to vary the timing of peak finger height confirmed that the effect of DAF on timing variability is directly influenced by the finger trajectory.