Critical flicker frequency of mentally retarded and normal persons.

Critical flicker frequency (CFF) of 40 men, 20 mentally retarded whose mean age was 22.0 yr. and 20 normal whose mean age was 21.5 yr., was measured under binocular viewing using the Lafayette Visual Perception Control with a display unit. Subjects had been previously tested for visual acuity and color blindness. Analysis showed a significant difference in CFF between mentally retarded persons and normal individuals, the former having lower CFF than the latter. This finding suggests lower perceptual sensitivity of the mentally retarded persons. Further research with provision for EEG recordings is suggested.