Figure 1.

A. Positions of the boundary markers for a typical shape are illustrated. A size bar representing 1 degree of visual angle is provided in the lower left corner of this panel. B. A sample from the full inventory was selected for display. For a given subject a random starting point was chosen, designated here by the arrow. Then proceeding clockwise, every Nth dot was selected to be in the display set. The value of N varied across shapes to adjust for difficulty. C. The dots of the display set are shown. Dot size has been enlarged for purposes of illustration.