Abstract
The body reaction time of mental retardates was investigated with respect to the effects of aging and intellectial ability. The subjects ranging in age from 6 to 49 years and in the intellectual qoutient (IQ) from 14 to 115, tried to jump vertically responding to the flashing light. The body reaction time was measured from the mechanogram and divided into the following two components: the time from the onset of stimulation to the beginning of the knee extension (the premotor time), and the time from the beginning of the knee extension to the onset of toe-off from the foot plate (the motor time).
The mean body reaction time and the two components of the retarded subjects were greater than the norm in non-retarded population. The distribution of reaction times by age showed a progressive decrease in incidence of the slower body reaction time or the slower premotor time with increasing age. Any age-related changing of the motor time were not observed. In the adult subjects, there was positive relationship between the body reaction time or the premotor time and IQ score. The motor time was not consistently related to IQ. It was found that the shortest reaction time of retardates in any age or with any grade of IQ was on level with the norm in non-retarded population.
