Effects of path angle changes on the times for ballistic and visually-controlled two-component arm movements

- PMTS generally ignores changes of path angle in movements.
- Effects are small when there is an intervening target.
- With no intervening target, effects are significant.
- Ballistic movement effects are large compared to visually-controlled moves.

Although several Predetermined Motion time Systems mention the effects of change of path angle during a movement, there does not appear to be any experimental evidence for the quoted effects. Here we report effects of angle changes between zero and 180° during the movement, with and without an intervening target at the end of the first component of the movement. The effects are variable: with ballistic movements without an intervening target there is an increase of MT with path angle change; when there is an intervening target the MT of the first component decreases with change of path angle, while that of the second component increases, so that the total movement time is independent of the change in path angle. When the movements are made under visual control, with no intervening target, MT increases with change of path angle, whereas when there is an intervening target, there is no effect of change of path angle, either on the first or second component of the movement. Thus the occurrence of movement time increments is dependent on the form of motor control and the way in which the path angle change occurs.