Space-time invariance in handwriting: Contrasts between primary school children displaying advanced or retarded handwriting acquisition

Previous research into the handwriting of adult subjects has highlighted the possible roles of ‘relative timing’ (Viviani and Terzuolo 1980) and simple oscillations (Hollerbach 1981) in controlling movement. Both of these factors provide interesting perspectives with which to view the development of fine motor control in children. The spatio-temporal structure of writing movements was examined between children with refined handwriting skills and those exhibiting unusually poor writing for their age. The analysis concentrated on three sites of temporal variability: absolute timing, temporal patterning, and rhythmic content of the writing movements. The results supported the notion that the relative timing of segments within a movement sequence acts as a major constraint on motor output variability. It is suggested, however, that previous simplistic views of ‘relative timing’ be expanded, and that such timing may be dictated by optimisation strategies. Differences in the stability of the graphic product between groups could not be accounted for by differences in the rhythmic content of the movements. In the absolute timing of writing tasks, the results suggest that variability in writing time from trial to trial, and duration of intra-task pauses, are better indicators of writing difficulties than total writing time or the number of pauses.