The cutoff for veridical orientation discrimination is derived fro the psychometric function for 4AFC orientation discrimination. Dotted line in the figure is the prediction when the cutoff for direction is the same as the cutoff for orientation.
Solid line is the linear regression line of all data points.
At 20 deg eccentricity, the cutoff for veridical orientation perception is higher than that for veridical motion perception, reflected from the figure that most of the data points for 20 deg are below prediction line. At 30 deg eccentricity, the cutoff for orientation is close to that for direction, reflected from the scatter plot that most of the data points for 30 deg are close to the prediction line. At 40 deg eccentricity, the cutoff for orientation is lower than that for direction, reflected from the scatter plot that most of the data points for 4 deg are above the prediction line.