Figure 1.

Top: MDF stimulus showing a horizontal rectangle defined by 100% coherently moving dots moving upward inside of a central horizontal rectangular area and 100% coherently moving dots moving downward outside of the rectangular area (i.e., a long spaceship). Bottom: The stimulus appearance when motion coherence is reduced to 75%; 25% of the dots are moving in random directions both inside and outside the rectangular area. Yellow dotted lines are not present on the display during testing; they have been added to the figure only to highlight the rectangular borders of motion contrast.