Figure 1.

Experimental Setup. (A) Shows the experimental setup for the orientation constancy task (classification of line orientation angle independent of head tilt; the horizontal line shown is 90°). To perform the orientation constancy task, the subject sits in the right chair and determines the angle of the line placed on the board in one of six orientations (vertical, horizontal, −22, 22, −45, and 45° relative to the vertical; 6AFC). (B) Shows the experiment setup for the length constancy task (classification of line length independent of line orientation angle). To perform the length constancy task, the subject sits in the right chair and determines the length of the line placed on the board in one of four orientations (vertical, horizontal, −45, and 45° relative to the vertical; 5AFC) (during each task only one bar is placed on the board).