When are two hands better than one? A Study of Bimanual Interaction
Benjamin Schmidt
Department of Computer Science
University of Canterbury
In everyday life people skillfully use both hands in complex tasks such as driving a car or drawing a picture. However, when attempting tasks on a computer, we are normally restricted to using our dominant hand for direct manipulation. Bimanual interaction is the study of how systems can be de- veloped to allow users to take advantage of their capacity for skilled bimanual interaction.
Four design principles for developing bimanual interaction systems are distilled from a review of the current research. Principle One discusses the importance of understanding how people perform bimanual actions. Principle Two discusses what type of devices and actions should be used. Principle Three describes how bimanual interaction techniques can be used to eliminate modes. Principle Four discusses how bimanual interaction techniques can be used to increase usable screen space and reduce time to target and attention switching.
The principles are used to develop two systems (Bi-DM and Bi-Draw). These systems are evaluated with their equivalent traditional unimanual sys- tems (Uni-DM and Uni-Draw). Bi-DM was slightly faster than Uni-DM though the di erence was just outside the 95% signi cance level. Bi-Draw was signi cantly slower than Uni-Draw. The users were required to complete the tasks approximately. An experiment with an expert user of Bi-Draw showed that similar times to Uni-Draw can be achieved.
These results disagreed with prior work that showed bimanual interaction systems are more e cient than their equivalent unimanual versions. A third experiment based on earlier work was conducted. The users were required to complete tasks with a high accuracy level. Comparing the results from this experiment to the one on which it was based indicates that the low quality of the non-preferred mouse was probably responsible for the poor performance of our bimanual systems. Other likely factors detrimentally a ecting the bimanual results include the low accuracy required for completing the tasks and the short training periods.