Context and motor control in handwriting

Abstract

Three experiments are described which examine the muscle variables controlled in writing the letters e and l. These demonstrate, subject to the number of letters being written, that each size and type of letter is characterised by a specific maximum velocity. The muscle variables used to produce these velocities are influenced by context. In experiment 1, where subjects wrote single letters (a null context), the same muscle variable, force, is controlled to produce different letters of different sizes. In experiment 2, subjects wrote two identical letters (a repetition context) and, in this case, the control variable was force for letter type but magnitude and duration of force for letter size. Analysis indicated the importance of letter position rather than repetition per se. Accordingly, experiment 3 sought to manipulate context directly by contrasting a repetition and an alternating context. Context was effective and influenced the way individuals attained a particular Vmax. A theoretical mechanism is proposed that accounts for this outcome.