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 diffe
rence in CFF between mentally retarded persons and normal individuals,
the former having lower CFF than the latter. This finding suggests lo
wer perceptual sensitivity of the mentally retarded persons. Futher re
search with provision for EEG recordings is suggested.