Fitts' law, relating the time to acquire a target to the target size and the distance from the target, is an effective and widely used predictor of performance in feedback controlled human motor targeting tasks. Beyond target size, however, movement time also varies according to a subject controlled mental tradeoff between speed and accuracy for a given task. To adjust for this trade-off, researchers often use the "effective target width", the target width normalized for variations in movement speed, as a predictor of movement time. In this paper, we describe on-going work on analyzing factors affecting the speed-accuracy tradeoff for Fitts' tasks in subjects, exploring both incentives and penalties to manipulate subject accuracy. We also describe our work on measurable parameters of motion that correlate with the speedaccuracy trade-off. Keywords Fitts' Law, Signal, Speed, Accuracy ACM Classification Keywords H5.m. Information interfaces and presentation (e.g...