Delayed Handwriting

Human sensory and motor activities are apparently rather closely coupled. Sensory information is the primary regulator or controller of many motor acts. This regulation is mediated by complex feedback mechanisms which may act through several sensory modalities simultaneously. Interruption or blockage of some of these paths may produce little or no alteration in the motor behavior being monitored. If, however, the sensory information itself is being transformed or modified, e.g., by distortions such as inverting lenses for the eyes, or, if different sensory pathways yield conflicting information, motor disturbances may be induced, e.g., interference from delayed auditory feedback. In this type of distortion, speech uttered by S is returned to him via earphones after a certain delay. The interference with normal speech production is considerable; S becomes confused, he speaks haltingly, and if he is required to read aloud from printed text, he makes articalatory errors which he seems unable to avoid. These articulatory errors are classified by Fairbanks and Guttman ( 1) into four classes: substitution, omission, addition, and a miscellaneous category. They further subdivide additions into repetitions and insertions (nonrepetitive). Fairbanks and Gutunan also find that the time taken by S to read a standard passage increases as the amount of delay is increased. The articdatory disturbances reach a maximum at about 200 msec. delay. Recently, experiments in which Ss heard the delayed sounds of their own finger tapping ( 2 ) have demonstrated similar effects. The existence of a telewriter, which can reproduce the track of a stylus point on a separate viewing surface by generating voltages corresponding to X and Y coordinates of the stylus, raised the possibility of introducing various delays between the act of writing and the appearance of the script. This brief experiment investigates the motor disturbances generated under this condition.