Assessment of Fitts’ Law for Quantifying Combined Rotational and Translational Movements

Abstract

Objective: To develop a model for human performance in combined translational and rotational movements based on Fitts' law. Background: Fitts' law has been successfully applied to translational movements in the past, providing generalization beyond a specific task as well as performance predictions. For movements involving both translations and rotations, no equivalent theory exists, making comparisons of input devices for these movements more ambiguous. Method: The study consisted of three experiments. In the first two, participants performed either pure translational or pure rotational movements of 1 degree of freedom. The third experiment involved the same movements combined. Results: On average, the performance times for combined movements were equal to the sum of the times for equivalent separate rotational and translational movements. A simple Fitts' law equivalent for combined movements with a similar slope as the separate com-ponents was proposed. In addition, a significant degree of coordination of the combined movements was found. This had a strong bias toward a parallel execution in 12 out of 13 participants. Conclusion: Combined movements with rotations and translations of 1 degree of freedom can be approximated using a simple Fitts' law equivalent. The rotational and translational components appear to be coordinated by the central nervous system to generate a parallel execution. Application: The results may help drive human interface designs and provide insights into the coordination of combined movements. Future extensions may be possible for the movements of higher degrees of freedom used in robot teleoperation and virtual reality applications.

How do children adapt strategies when drawing on a tablet?

“…In addition, drawing itself requires a translational and rotational movement or a combination of ongoing movement for both. Fitts law seems to fit well in most discrete pointing movement [17] but not on ongoing movements [3].…”

Orientation matters

“…We decided to use only two values for translation and rotation to keep the experiment feasible. A similar design was used by Hoffman et al [4] and Stoelen and Akin [11] who also used 16 configurations. The difficulty of each configuration (Table 1) was measured using the Index of Difficulty (ID) with the Shannon formula because it always gives a positive rating for the index of task difficulty [8].…”

“…Stoelen and Akin show that rotation and translation have the same difficulty and complexity which may indicate that parallel execution is efficient [11]. They used a magnetic sensor system instead of multitouch.…”

Similar Mechanisms of Movement Control in Target- and Effect-Directed Actions toward Spatial Goals?

“…Fitts’ Law holds for bimanual tasks as well as tasks performed by dyads (Mottet et al, 2001). Further, Fitts’ Law can be applied for translational as well as rotational movements (Stoelen and Akin, 2010) and has been studied intensively for distant aiming tasks with computer devices (Kopper et al, 2010). Whereas most studies investigated pointing and aiming with discrete tasks (for a review see Elliott et al, 1991), in some studies continuous tasks were used (e.g., Mottet et al, 2001).…”