Heart rate and reaction times for mentally retarded and nonretarded adults in subject- and experimenter-initiated tasks.

Reaction time (RT) and heart-rate measures were obtained for 10 retarded (mean IQ = 65) and 10 nonretarded young adults. Each subject initiated half of the trials themselves. The other half were initiated by the experimenter. These trials were distributed over preparatory intervals of 2-, 4-, and 8-second durations. We found that all subjects, when initiating the trial themselves, reduced both mean RT and response variability. Heart-rate patterns were similar for both intelligence groups on experimenter-initiated trials, but were markedly different when subjects initiated the trials themselves. Results suggest that self-initiated trials may benefit retarded subjects by overcoming some attentional problems, but difficulties with utilizing successful response strategies remain.