Functions of vision in the control of handwriting

Abstract

Much recent work on handwriting has emphasized the organisational processes which occur before output and has minimised the role of feedback processes, although reports of dysgraphic patients suggest that such processes have an important role in control. In the experiment reported here subjects wrote a set of sentences in each of six conditions, three with sight of the hand, and three without. In each visual condition subjects wrote normally, while counting aloud, and while repeating a nonsense syllable aloud. The orientation of the written words to the horizontal was affected by the loss of vision rather than by the addition of a secondary task, but the errors produced during writing were very similar for the secondary task condition and the without-vision condition. Errors occur at several levels in the output system which suggests that the role of sensory feedback is a complex one. Editing or monitoring functions can be compared with place keeping or sequencing control functions but current models are not well enough specified to help us discriminate between these.