Electrical blink reflex habituation in mentally retarded adults

Electrophysiological methods of studying the habituation of the blink reflex have been used, to document by objective means the lack of habituation of the blink reflex in mentally retarded adults. Habituation of the blink reflex to sets of stimuli with decreasing interstimulus duration, which is fixed in each set of stimuli, has been studied in normal human volunteers and mentally retarded subjects. Habituation of direct and indirect R2 has been poor or absent in the mentally retarded subjects. The habituation indices of mentally retarded subjects do not overlap the habituation indices of the normal volunteers. In significant numbers of retarded subjects no habituation of the indirect R2 (P less than 0.00001) and of direct R2 (P less than 0.0005) was noted. No significant difference in habituation of the direct R2 and indirect R2 is noted in normal volunteers.