Violations of Fitts’ Law in a Ballistic Task

ABSTRACT

The authors explored changes in the postural preparation and movement times during jumps into targets of different sizes placed at different distances from the participant. Both movement and preparation times scaled with movement distance. Neither movement nor preparation time showed an effect of target size, although preparation time showed a tendency to increase for smaller targets. These observations show that the classical Fitts’ law can be violated in tasks that involve a ballistic component. The data corroborate a hypothesis that Fitts’ law originates at the level of movement planning.

Keywords:

• Fitts’ law
• jumping
• postural adjustments
• speed–accuracy trade-off

ACKNOWLEDGEMENT

This work was partly supported by National Institutes of Health grant NS-035032.