The influence of tremor on handwriting performance under conditions of low and intermediate physical stress

This study used a temporally sensitive technique (coherency analysis) to examine individual differences in handwriting dynamics of people with and without tremor, under conditions of low and mild physical stress. Participants with tremor maintained their axial pen pressure (APP), while those without tremor increased their pressure in conditions of mild stress. Both groups wrote at a similar speed with a small but significant increase in the stress condition- The between-trial coherency (i.e. temporal similarity) of velocity and APP profiles was greater for people without tremor. When writing in mildly stressful conditions, the coherency increased for people without tremor but tended to decrease or be maintained for people with tremor. These findings may be applied in the future to finding clues to the authenticity of documents written by people with tremor. The results are discussed in terms of the neuromotor noise theory.