Overview  

A trackball is a computer input pointing device that consists of a ball held by a socket containing sensors to detect a rotation of the ball. Trackballs often also have a few buttons to make selections on screen. A user rolls the ball to position the on-screen pointer, using their fingers, or more commonly the palm of their hand, while using their fingertips to press the buttons. Compared to a mouse, the most common computer input device, a trackball has no limits on travel. Sometimes during computer navigation, a mouse can reach the edge of its working area while the user still wants to move the screen pointer farther. With a trackball, the user simply continues rolling, whereas a mouse would have to be lifted and re-positioned. This helps with tasks such as drawing and creating diagrams (Accot & Zhai, 1999). While trackballs were used in early laptops and by digital designers in the 1990-2000s, trackballs have almost entirely been replaced by touchpads.

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One study that compared a touch input, stylus input, and trackball input on on-screen keyboarding tasks found that while stylus input was the most accurate and quickest overall, when the on-screen keyboard keys were small, the trackball was the most accurate device (Schedlbauer, 2007). Comparing stylus input and trackball input between sitting and standing conditions, the same authors found standing increases time-to-complete task and error rates for trackball use, but that standing did not affect performance when using a stylus (Schedlbauer, Pastel & Heines, 2006). A study by Revelle and Strommen (1990) found that when 3-year-old children were given 5 sessions of practice with a joystick, a mouse, and a trackball, the error rates for the mouse input declined significantly across the 5 session, while error rates for trackball and joystick inputs did not decline over time. This implies that young children may continue to struggle to use trackballs and joysticks even with practice, while they seem to be able to learn and improve their mouse input skills with practice. However, a more recent  small scale study found that a trackball with revised software drivers proved to be an effective input device for two children with multiple disabilities (Shih & Shih, 2010). While mainstream trackball use has declined drastically over the past 25 years, their use as an assistive technology for students with disabilities may have potential. However due to the scarce amount of evidence to demonstrate their efficacy, users may want to consider other tech options.

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Research Rating: While there is some experimental research on the use of trackballs as an assistive technology, these claims would be strengthened by further  larger-scale studies.

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Advantages:

• Cursor travel on-screen is not limited by the workspace available for input device movement

• Potentially a viable option for computer-input for people with multiple disabilities (Shih & Shih, 2010)

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Disadvantages:

• Errors in selection remain for young children users even after 5 session of practice (Revelle & Strommen, 1990)

 

To Consider

• Many other input devices are available (see <Fine Motor>). Contact an Occupational Therapist to determine which system and what settings are the most appropriate for an individual user.