ABSTRACT
This chapter introduces some tools for building more detailed descriptions of the time evolution of the movement. The predicted movement times for different experimental conditions can be read from the graph as the time coordinates for the intersections of the target edges and the movement time history. The function that results will be consistent with P. M. Fitts’ Law. Most biological control systems will have characteristics of both lags and time delays in their response to external stimuli. With respect to movement time, both the limited capacity communication channel and the first-order lag metaphors are equivalent in providing models for the data from Fitts’ experiments. It could be argued that the first-order lag does not directly account for the variability in the distribution of movement endpoints within the target. However, a stochastic element could be added to the model, such that the “effective step input” is probabilistically related to the actual experimental constraints.
