In this paper we investigate the dynamics (including velocities and accelerations) of mouse pointing when Pointer Acceleration (PA) functions are used. We also propose a simple model for these dynamics from a control theoretic perspective. The model allows us to simulate the effect of PA functions on pointing dynamics. In particular, it reproduces and explains many important phenomena we observe in pointing dynamics with PA functions. These include: (1) Pointer position, velocity, and acceleration over time, (2) Different accelerations when moving in different directions, and the resulting mouse drift when using PA functions, (3) Discontinuous jumps in phase space and associated acceleration peaks in Hooke plots when using Step PA functions. We identify parameters of the model using a reciprocal pointing task with the mouse controlling a pointer on a computer screen using sigmoid and step PA functions and constant gain. Our model explains the human-computer system including the PA function as a closed-loop dynamical system. In particular, we use a second-order model resembling a spring-mass-damper system (second order lag). Our model explains and allows to simulate the role of PA functions in pointing, including the phenomena described above.

Bibtex:

Jörg Müller
Aarhus University
joerg.mueller (at) acm (dot) org

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