Figure 4.

Human psychophysical length-discrimination measurements of visual masking effects from 11 human subjects using nonoverlapping masks of varied duration (100, 300, or 500 ms). (a) The appearance of the stimuli during the course of a psychophysical trial. (b) SOA here represents the period between the onset of the mask and the onset of the target (and so has the opposite meaning than in Fig. 2). Masks (two 6° tall bars with a width of 0.5° flanking each side of each target) appear at time 0, and targets can appear earlier (backward masking), simultaneously, or later (forward masking), in 50-ms steps. Targets were black and presented for 10 ms duration, and masks were flanking black bars that abutted the target. Notice that target visibility is most greatly affected when the masks turn on and off.