Fig. 7.

Reaction times and vigor of reaching and evaluation of the hypothesis that the movement characteristics of each subject are related to a traitlike vigor. A: hand velocity profiles for subjects that moved their arm with high or low vigor. Low-vigor individuals appeared to start their movements later with respect to the onset of the visual stimulus. Shaded areas are SE. B: relationship between arm vigor and arm reaction time (R = −0.33, P < 0.05). C: hypothesis that a single latent variable, trait vigor, may account for the various measured variables in each subject. For each subject we computed the likelihood of his/her data given this hypothesis and then computed the posterior probability of the hypothesis given the data. The distribution of the posterior probabilities is shown (the null hypothesis, i.e., no trait vigor, has a probability of 0.5).