Discriminability of differences in line slope and in line arrangement as a function of mask delay

Position uncertainty was used to guarantee that an S’s attention was distributed equally over a visual display. Diminishing discriminability through a masking flash, which controlled the time available to attend selectively to the individual figures in the display, increased the relative discriminability of figures differing in their line slope as compared to figures differing in their line arrangement. Diminishing discriminability through decreasing the clarity of a visual trace by reducing exposure duration did not increase the relative discriminability of figures differing in their line slopes. It is suggested that the discriminability of differences in line slope and in line arrangement varies with the distribution of attention. The results are interpreted as supporting the hypothesis that, under distributed attention in peripheral vision, the visual system is more sensitive to differences in line slope than to differences in line arrangement.