Planning and timing of finger-tapping sequences with a stressed element.

Advance planning and execution-time organization of sequences of five finger taps were studied in four experiments. Intertap intervals were required to be equal. In some experimental conditions, one of the taps had to be stronger than the other four. Serial position of the stressed tap, number of alternative stress positions, and tapping rate were manipulated. Time to initiate the sequence after presentation of a reaction stimulus (RT), intertap intervals, and force of the taps were measured. the different effects of stress production and choosing between alternative stress locations on the RT of fast as compared to slow sequences suggest that a plan was selected and activated for the whole sequence only when it had to be executed at a fast rate. Additional organization of the fast sequences during execution was inferred from the intertap intervals, force patterns, and stress location errors, that were all different from those observed in slow sequences. The effects of stress production on timing are discussed in relation to existing timing models.