The effects of motor complexity and practice on initiation time in writing and drawing.

A large number of reaction-time studies have shown that more complex movements require more advance programming than simpler movements, thereby increasing initiation time. In handwriting experiments, however, increases in initiation time as a function of the number of strokes tend to be very small or nonexistent. This may be caused by the well-practiced nature of letter writing and the level of advance programming. To investigate this, we conducted an experiment in which subjects had to copy, as quickly as possible, stimuli consisting of three categories. Not only letters but also figures and patterns were used, consisting of familiar figures and novel nonsense (unfamiliar) patterns which were both rarely or never drawn before. These stimuli were presented on a computer screen; writing and drawing movements were recorded by means of an XY-tablet. Initiation time was found to increase linearly with the number of strokes--which varied from four to ten--but the effect was much larger for figures and patterns than for letters, and rapidly decreased with practice (successive presentations). In order to try to eliminate a difference in initiation time on account of perceptual processing, the same stimuli were presented again, but had to be written and drawn in another style, which differed only in motor complexity (the number of strokes had to be doubled by requiring the subject to draw each line twice). Drawing double lines increased initiation time with increasing number of strokes significantly for the figures and patterns. For letters, the increase was irrespective of the number of strokes. These results suggest that the planning of a movement sequence involves several levels and that the amount of preprogramming is highly influenced by the amount of motor practice.