A 'Speed-Difficulty-Accuracy' Model Following a General Trajectory Motor Task with Spatial Constraints: An Information-Based Model

Accuracy in executing a motor task, i.e., in following a given trajectory under geometrical constraints, is of great interest in work operations as well as in biomechanics applications. In the framework of the Fitts' law research on motor tasks, experimental studies usually refer to simple trajectories which are of low interest in practical applications. Furthermore, available models lack predicting accuracy in executing motor tasks since do not systematically investigate effects of both speed and task difficulty (index of difficulty (ID)). In this paper, the authors propose a 'Speed-ID-Accuracy' model aiming at overcoming abovementioned limits. The model is of general validity as is based on an information-based formulation of a trajectory ID; the model proposed put into relation accuracy in task execution with a general trajectory and with the speed of task execution. Modeling accuracy, defined as standard deviation of the endpoint position, is carried out by regressing data available in the literature. The model proposed proves to be more accurate than the classical 'Speed-Accuracy' model in fitting available data. Such a result has been found in both numerical cases relating to 'tunnel' and 'circular' traveling tasks. Limits of data from field experiments are stressed out and future research field of investigations in work environment and biomechanics are figured out.