As part of the redesign of the Microsoft mouse by Matrix Product Design, a series of user tests were performed by ID Two. We used artificial tasks representative of typical mouse use allowing repeated measures of time and error.
The initial questions were about the impact on performance and preference of different mouse shapes, asymmetric buttons and moving the ball from the back to the front.
The first tests compared four designs on four tasks: maze tracing, Fitts' tapping, precision selection, signature writing. Significant differences on the maze task showed an advantage for the mouse with the ball in front.
Each test led to design changes. Most tests led to other tests either because of measured performance or further design insights.
The first tests raised questions about people actually hold mice. The second test, a two-day photo survey of over 60 users, showed users holding the mouse with their fingertips not palms. Next, a test of three different switch types showed preference for a sharp click. Tests of left-handed users showed no disadvantage with asymmetric buttons but revealed errors of accidentally pressing both buttons. Finally, adding a ridge between the buttons was shown to eliminate this user error.
Key innovations either discovered or confirmed by the testing included: fitting the mouse to finger tips not palm, moving the ball from back to front for better feel and performance, using asymmetric buttons as a more obvious coding for frequency of use, and adding a ridge between the buttons to prevent accidentally pressing both.
Source: Abstract