Figure 1.

Schematic of the procedure for Experiment 1. In the component field (left), individual gratings alternated every second, and in the compound field (right), the compound stimulus alternated with a blank field every second. Note that for convenience these are depicted as alternating at the same times. In the actual experiment, the relative temporal phase of the alternations in the two hemi-fields was given a random offset that differed every trial. For this experiment, the reference probe contrast was fixed at 42% and the test probe contrast (compound side) was varied according to a staircase procedure to find the PSE. The probe stimuli consisted of compound stimuli with the same orientation as the adapting stimuli. On each trial, observers indicated which probe stimulus appeared to have the higher contrast. Each observer performed a minimum of four staircases for each adapting configuration.