Intrasubject response variability in relation to intelligence.

2 studies compared intraindividual response variabilities of normals and retardates. In the 1st, involving a reaction time procedure, individual retardates were both slower and less consistent in their reactions. In the 2nd study, employing a short-term memory task, the mentally subnormal individuals were less accurate and more variable than normals. Variability of both groups increased as retention interval increased. These results indicate that the performance of mentally retarded 5s is characterized as much by inconsistency as it is by a low level. Increased intra-S response variability within certain deviant groups may have implications for an understanding of pathological processes.