SPACE-TIME INVARIANCE IN ADULT HANDWRITING

Handwriting quality is commonly evaluated off-line using either subjec tive or pattern recognition techniques based on the static final outpu t. Skilled performance is characterised in terms of legibility and as a minimisation of spatial variability. However, these techniques are s ubject to error, and provide little information about the underlying d ynamics producing the movement. This study employed temporally sensiti ve techniques to investigate the relationship between spatial (i.e. le gibility) and the kinematic (i.e. dynamic) aspects of handwriting prod uction. Each of 18 adult subjects (7 male, 11 female) wrote the pseudo -word MADRO-NAL 10 times in their natural cursive handwriting. Horizon tal (x), vertical (y) and pressure (z) coordinate data were collected using a Wacom 1212-R graphics tablet controlled by a laboratory comput er. Spatio-temporal aspects of the x, y and z velocities of the stylus were analysed both between trials and within subjects using coherence analysis. Subjects previously rated as good handwriters by three inde pendent judges displayed a greater degree of temporal consistency than the less proficient writers. The results showed that spatial inconsis tencies are related to dynamic variability and demonstrated that the m ethodology employed can provide a useful tool for the quantitative ass essment of handwriting quality. (C) 1997 Elsevier Science B.V.