Performance on a reciprocal tapping task with variations in intertapping interval.

Fitts' law was investigated in a study of the effect of the index of difficulty (ID) and intertapping interval upon reaction time (RT) and movement time (MT) for a reciprocal tapping task. ID showed its well-established relationship with MT as described by Fitts' law: MT = aID + b. Improvement in the linearity of this relationship was, however, demonstrated by expressing MT in logarithmic units. While ID had an unsubstantial (though significant) effect on RT, increases in intertapping interval from zero to any level of discrete tapping led to significant increases in RT of about 135 msec. The results are interpreted as lending support to Fitts' thesis that RT and MT reflect independent phases of information processing.