ABSTRACT. The present authors tested the assumptions in R. S. Woodworth's (1899) 2-component model regarding the specific roles of vision in the production of both the initial impulse and the error-correction phases of movement. Participants (N = 40) practiced a rapid aiming task (1,500 trials), with either no visual feedback, vision of only the 1st 50% of the movement, vision of only the 1st 75% of the movement, or vision of the entire movement. Consistent with previous research, the availability of vision over the 1st half of the movement had no effect on aiming accuracy during ...

<.001. Post hoc comparisons indicated that the FV group had slower MTs than the other three groups (see Figure 1b). No interactions for ln(RMSE) and total MT were significant (p><.001. Post hoc comparisons revealed that initial impulses were less variable for the FV group than for the other three groups, whereas the 75%V group was less variable than the 50%V and the NV groups (see Figure 2). No significant effects were observed for initial impulse MT (p><.001. A breakdown of that interaction indicated that there was a significant increase in variability for all visual conditions up to peak negative acceleration (see Figure 4). There was then a reliable decrease in variability from peak negative acceleration to the end of the initial impulse for the FV condition but not for the 75%V, 50%V, and NV conditions. A nonsignificant three-way interaction between visual condition, kinematic index, and day, F(3, 36) = 2.0, p>