Fig. 1.

Mean reaction times (RT) and accuracy rates (% correct) as a function of A) group (Tourette syndrome, healthy controls), B) correspondence (corresponding, noncorresponding) and C) the interaction between group and correspondence. All participants show a slowing of RT and reduction in accuracy for noncorresponding compared with corresponding trials, confirming that incorrect motor impulses interfered with selection of correct responses and sometimes captured the response system sufficiently to produce errors. The Tourette syndrome group showed greater mean interference effects on RT; however, unlike the distributional analytic methods described in the captions of Figs. 2 and 3, mean effects cannot distinguish the strength of the incorrect prepotent motor action from the proficiency of inhibiting this action. Error bars reflect standard errors of the mean.