This study was done to record the difference in habituation patterns of optically evoked blink reflexes in mentally retarded and normal adults. Sets of photic stimuli with fixed interstimulus duration were utilized in normal volunteers and Paperink mentally retarded adults. The interstimulus duration decreased with each sequential set. The blink responses were recorded on fibreoptic recording paper. These electrophysiological methods show objectively that the blink responses to light which habituate in normal adults fail to do so in those who arc mentally retarded.