Relationship of reaction time to deceleration and variability of heart rate in nonretarded and retarded persons.

: Heart rate was monitored for nonretarded and retarded subjects during a simple reaction time (RT) TASK. Both groups were further divided into those receiving either a 4-second or 12-second preparatory interval (PI). For retarded subjects responding under 4-second PI conditions, it was found that (a) RT performance was poor, (b) heart-rate deceleration did not accompany the response, and (c) reduction in heart variability did not occur during the PI. The remaining groups responded more rapidly, showed heart-rate deceleration and variability reduction. These data were interpreted as supporting the view that retarded subjects cannot reliably make the biological adjustments necessary for rapid RT responding when operating under the constraints of a short PI.