Possible outcomes of Experiment 2.

The first possibility is that matching the direction of the adapting and test stimuli leads to greater adaptation of perceived speed (first row). If this is the case, then the Opposite Direction condition should produce the highest PSE (smallest tSAE) and the Same Direction condition should produce the lowest PSE (greatest tSAE). This is because in the Same Direction condition, the direction of motion for the reference hand is matched at adaptation and test, whereas in the Opposite Direction condition, the motion for the reference hand at adaptation and test are in opposite directions. The second possibility is that the greatest adaptation occurs with an adapting stimulus moving in the opposite direction to the test (second row). In this case the Same Direction condition should produce the highest PSE (smallest tSAE) and the Opposite Direction condition should produce the lowest PSE (greatest tSAE). The third possibility is that the tSAE is insensitive to direction, with the adapting stimulus creating similar levels of adaptation regardless of its direction relative to test (third row). In this case, we would not expect to see any consistent differences across conditions.