Group I afferents of the forearm and hand evoke facilitatory reflexes to the scapulothoracic muscles (Alexander & Harrison, 2003 Exp Br R 148: 277-282). These reflexes assist in stabilising the shoulder girdle during precise use of the hand and are facilitated when doing a complex task (Alexander & Harrison, 2003 SFN 186.7). We have now investigated whether these shoulder girdle reflexes are dependent on mental effort. Reflexes were evoked in trapezius by electrically stimulating the ulnar nerve. With the same background EMG the reflex was evoked whilst performing a task in which washers were manipulated onto pegs using forceps. This required a degree of mental effort. Subjects were filmed whilst performing the task. In eleven subjects, the reflex was measured a) while performing the task, b) while the hand was held stationary in the same position whilst holding the forceps and c) while the hand was held in this position and the subject watched the film of themselves performing the task. While doing this t...