Two experiments, with 34 mentally retarded (MR) 16-33 yr olds (WAIS IQs 43-76) and 34 CA-matched normal controls, investigated whether differences in the way that MR and non-MR monitor and regulate speed and accuracy of responding contribute to the slower and more variable performance of MR Ss on choice RT tasks. In Exp I, most MR Ss detected their errors as efficiently as controls, a finding that excludes the possibility that MR Ss do not monitor accuracy efficiently but achieve comparable levels of accuracy by consistently responding within slow RT bands that minimize likelihood of errors. Exp II showed that while a qualitatively similar trial-by-trial tracking mechanism mediated the performance of both groups, MR Ss were less efficient at constraining RTs within fast but safe bands. Increasing error probabilities at longer RTs suggested that momentary fluctuations in stimulus discriminability and/or attention affected RT variability in MR Ss. The RT patterns for various sequences of correct responses initiated and terminated by errors suggested that the effective past experience guiding trial-by-trial RT adjustments of MR Ss was short and inadequate and that this accounted for much of the remaining RT variability contributing to differences between MR and non-MR Ss. (53 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).
- accuracy in choice RT tasks, mentally retarded 16-33 yr olds
- monitoring &
- regulation of speed &