Binary choice reaction time as a function of the relationship between durations and forms of responses

In a choice between responding with the left or right hand, some kinds of differences between the movements increase RT (Reaction Time) while others do not. Of the first kind are differences in form, while differences in the finger used are of the latter kind. In previous experiments differences in form were confounded with differences in duration. Since there is some indication that a difference in duration is sufficient to lengthen RT, both characteristics were varied separately. It turned out that a difference in form (duration being constant) has essentially the same effects as a difference in duration (form being constant): Mean RT is longer, variability of RT and MT (movement time) is larger, and frequency of choice errors is smaller than in choice between identical movements. These effects, which seem to be associated with choice between movements of different temporal patterns, are interpreted in terms of advance specification of movement parameters. Additional results on the relationship between response duration and RT suggest that RT does not depend on duration (or velocity) per se, but on how much the duration deviates from quickest performance.