Figure 1.

Trial sequence for the contrast adaptation paradigm. The test stimulus was a Gabor that appeared in one of four possible locations at a contrast that varied across trials. Trials consisted of either the test stimulus (baseline condition) or the adapter (a 2 × 2 grid of Gabors at 50% contrast) followed by the test stimulus after a time delay (post-adaptation conditions) during which the background luminance was displayed. The intertrial interval was 1 second for all conditions. Participants pressed a key to indicate the location of the test stimulus.