Directional probability information and Down syndrome: a training study.

In previous studies we have found that subjects with Down syndrome did not respond to changes in directional probability within a complex motor task in the manner of other subjects with mental retardation (Blais & Kerr, 1986; Kerr & Blais, 1985). Only after extended practice were significant changes noted in their reaction time (RT) performance; however, movement time (MT) data remained relatively unchanged (Kerr & Blais, 1987). In the present study, subjects were given training relative to the directional probability component of the task (choice of direction). The subjects with Down syndrome did improve their subsequent performance, but primarily in terms of MT. Although they did adopt a pattern of responding to changes in directional probability (RT) similar to that of subjects without mental retardation, the nature of the change reflected the extent of previous exposure to the task.