Low-frequency periodicity in the coordination of progressive handwriting

The paper addresses the question how the effector segments are coordinated during handwriting, in particular as a function of the left-to-right progression within words. It studies the phase relations between wrist and finger-joint rotations during a repetitive graphic task (long words consisting of letters 'e'), and it subjects the resulting continuous phase-relation plots to autocorrelation analysis. A novel phenomenon, viz. that of low-frequency (1-Hz) periodicity, is observed which presumably reflects adjustments of the coordination pattern about once per second, i.e., after every three or four letters 'e'. Moreover, word length and word position are found to affect this periodicity in a predictable manner. These results are related to those of an earlier study which used an ad-hoc method of analysing wrist-finger coordination adjustments. The paper underlines the value of phase-relation analysis for certain graphic tasks, but it also points out its limitations for this purpose.