One important factor influencing the accuracy of a timing estimate is the counting activity that a human subject may adopt. In the present study, the usefulness of this activity is evaluated with a strategy whereby subjects are presented segmented and nonsegmented intervals, before they start to produce a series of these intervals, using a finger-tapping procedure. The results are mainly analyzed in the light of Killeen and Weiss's (1987) model, which addressed this question of counting. The results revealed that (1) a scalar property gives a better description of the pacemaker activity than does a Poisson process, and (2) an optimal timing performance would be reached with the utilization of subintervals with an approximate value of 400 msec. Finally, the discussion also incorporates an analysis of the variability related to the motor component in a tapping task.