Effects of auditory feedback on velocity extrapolation by mentally retarded and nonretarded groups during rotary pursuit tracking.

Retarded adolescents, CA-matched nonretarded adolescents, and MA-matched nonretarded children stylus-tracked an intermittently disappearing rotary pursuit target with and without auditory feedback. Under the no-feedback condition, all groups demonstrated an almost linear increase in deviation errors over five successive 2-second intervals following disappearance of the target, with the retarded group showing a greater increase than did the CA-matched and MA-matched groups. Under the feedback condition, the CA-matched group reached an asymptote of target proximity 4 seconds after the target disappeared, whereas errors for the retarded and MA-matched groups continued to increase throughout the 10-second sample period. Performance of the retarded group with no feedback was interpreted as evidence for deficient velocity extrapolation, and failure of the retarded and MA-matched groups to stabilize proximity under the feedback condition was attributed to delayed response of the feedback.