Effect of Age and Parkinson's Disease on Cursor Positioning Using a Mouse
Simeon Keates, Shari Trewin · 2005 · Proceedings of the 7th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '05) · doi:10.1145/1090785.1090800
Summary
This paper presents a detailed empirical study examining how age and Parkinson's disease affect the ability to perform point-and-click tasks with a computer mouse. The researchers recruited 24 participants across four groups: young adults (ages 20-30), adults (ages 35-65), older adults (ages 70+), and adults with Parkinson's disease (ages 48-63). Participants completed a repeated-measures pointing task involving three target sizes (16, 32, and 64 pixels) and three target distances (192, 384, and 768 pixels) at random angles. The study goes beyond simple Fitts's Law analysis, which can show that performance differences exist but not why they exist. Instead, the authors use a comprehensive set of cursor movement metrics — including target re-entries, task axis crossings, movement direction changes, path length ratios, and missed clicks — alongside pause analysis and velocity profiling to build a detailed picture of how each group actually moves. The study employed both on-site and remote sessions, with remote participants using a specially designed program that provided auditory confirmation of successful clicks. Semi-structured interviews complemented the quantitative data, revealing 21 distinct mouse use difficulties and 12 compensatory strategies across the participant groups.
Key findings
Movement times differed significantly across all four groups (p<0.001): young adults averaged 1.02 seconds, adults 1.10 seconds, older adults 2.89 seconds, and Parkinson's users 1.91 seconds. The number of pauses per movement increased with age, with older adults averaging 4.70 pauses (>100ms) per movement compared to 1.40 for young adults. Parkinson's users fell between adults and older adults at 2.89 pauses per movement — consistent with their age group rather than showing a distinct Parkinson's-specific pattern. Peak velocity decreased with age, with Parkinson's users showing the lowest values at 1.94 pixels/msec (less than half the young adult value of 4.60). Critically, older adults used a fundamentally different movement strategy — many smaller submovements rather than the expected single ballistic move followed by a homing phase, suggesting that standard movement models developed for able-bodied users do not apply universally. The Parkinson's group showed a distinctive peak in pauses 250-300ms before button press, possibly indicating the mouse slipping during the click attempt. Both older adults and Parkinson's users showed an initial pause peak early in movement, suggesting an orientation phase before the primary submovement.
Relevance
This research has direct implications for accessible interface design. The finding that older adults and people with Parkinson's disease use fundamentally different cursor movement strategies than younger users means that accessibility features like target size adjustments, mouse sensitivity settings, and click assistance tools need to be designed with these different movement patterns in mind — not just as slower versions of the same movement model. The study's detailed metrics provide a framework for evaluating pointing device accommodations. For practitioners, key takeaways include: larger click targets help all groups, but the benefit mechanism differs by group; older adults need support for their multi-submovement strategy rather than just more time; and Parkinson's users specifically need assistance with the button-press phase, where tremor and rigidity cause the most difficulty. The work also highlights methodological challenges in researching motor-impaired populations, including small sample sizes and the heterogeneity of impairment effects.
Tags: motor accessibility · aging · Parkinson's disease · cursor control · mouse interaction · pointing devices · motor impairment · input methods · usability testing
Standards referenced: ISO 9241-9