Of 3 adjacent rectangular retinal areas, stimulated with the same intensity of light, the central area was stimulated for a short period, 4o, and after a lapse of time the flanking areas were briefly stimulated. Though the 3 areas were not illuminated at the same instant, the visual impressions were seen as simultaneous by the subject (i.e., provided the interval between the stimuli did not exceed 150o) and it was easy to compare the brilliances produced by the different areas, and to adjust the duration of the 2d stimulus until it produced a brilliance equal to that produced by the 1st. The 2d stimulus may be as short as 1/16 that of the 1st and still produce as much brilliance. This was shown experimentally to mean that the 2d stimulus depresses the activity aroused by the 1st.