Teulings, H.L. (1996). Handwriting movement control. In S.W. Keele and H. Heuer (Eds.), Handbook of perception and action. Vol.2: Motor Skills (pp. 561-613). London: Academic Press. ISBN 0-12-516162-X (reformatted).
Chapter 10
Handwriting Movement Control Hans Leo Teulings Motor Control Laboratory, Arizona State University, USA
1 INTRODUCTION
Among the many motor activities displacement of the body, maintaining posture, grasping and manipulating objects – handwriting distinguishes itself in that it is a learned and generally practiced human skill. For that reason, the motor control aspects of handwriting are both interesting and important. Being a learned skill, handwriting is related to typewriting, speech, sign language, and Morse coding. This chapter focuses on psychological, neurological, biomechanical, and computational theories of handwriting production and intends to draw parallels with these related skills, and especially with typewriting. Handwriting may have many features in common with these related motor skills so that a unified theory of these skills seems feasible. However, a unified cognitive theory of all motor skills, including grasping, posture, gait, jumping, or navigation is still lacking. This chapter intends to present the skill of handwriting, in the context of other motor skills and general motor concepts. However, handwriting skill includes only a limited domain of the basic motor skills. This may limit generalization of the knowledge of the handwriting motor system to other motor skills, but at the same time this limited domain allows simpler theories. The domain of handwriting skill is limited by the following basic features: (1) The aim is to translate a two dimensional graphical structure into a fixed sequence of movements. Performance is concerned mainly with the spatial structure rather than with the temporal structure. (2) Although seemingly continuous, the handwriting movement can be considered as a sequence of discrete actions, similar to the typewriting strokes. Namely, the handwriting movement forms a discrete sequence of ballistic movement segments, or handwriting strokes, which are executed at a near maximum rate of about 10 strokes per second, just like typewriting strokes. (3) Handwriting requires only small movement amplitudes (e.g., 0.5 cm), small flexions and extension, and small force levels so that biomechanical constraints are minimal.
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(4) The movement patterns are the result of an abstract motor program, which can be executed largely independent of visual feedback, proprioceptive feedback, friction, gravity, inertia, instructed speed, writing size, and muscles and limbs involved. Cursive script can be recorded using a commercial digitizing tablet connected to a computer. As the position of the pen tip on the tablet is digitized at a fixed, high frequency, all kinds of time functions such as positions, velocities, accelerations in horizontal and vertical directions can be estimated (Teulings &