Levels of Motor Programming in Writing Familiar and Unfamiliar Symbols

Rapid action sequences like the successive movements in speech, handwriting and other skilled motor activities, have to be planned or programmed before their execution. One class of data supporting such a view are reaction time data, in particular the effect of movement complexity on reaction time. In handwriting experiments this effect is not easily observed however. Five studies will be presented showing that at least one variable is crucial in this type of research: the amount of practice one has with the movements, or the familiarity of the movement pattern. The first two studies tried to find evidence for either the stroke or the letter as the basic unit of motor programming. In the third experiment the writing of novel symbols was contrasted with letter combinations of the same complexity. As expected, when only the first stroke of a character had to be written, the movements were initiated much faster. Unexpectedly this only held for the novel symbols. The overlearned letters could be initiated slightly faster than their first stroke. In the fourth study the number of strokes of the writing patterns was varied from two to seven. Choice reaction time increased with number of strokes for only the symbols, and not for the more practiced letters. In the final study only capitals had to be written in either the normal way, or an unusual way by adding spaces between the individual strokes. This unpracticed way of writing considerably increased reaction time. The combined results of these studies strongly suggest that the programming of motor commands proceeds on at least two levels, one for well-practiced movement sequences and one for novel movement patterns.