Thank you for participating in this experiment! You will be looking at stimuli rendered in 3d on our computer display and making 
judgments about the lightness of certain square target patches. You can think of "lightness" as "what color paint the patch is coated with". 

On each trial, you will see two squares ("contexts"), each consisting of a random assortment of grayscale rectangles. These two contexts are at a right angle to each other. You will also see a square near the center of the display. The square will be oriented in one of four ways: flat against the upper context, flat against the lower context, at a right angle to the upper context (and parallel with the lower context), and at a right angle to the lower context (and parallel to the upper context). This square is the target patch. 

To indicate your judgment about the lightness of the patch, you will use the palette to your right. Notice how each grayscale chip has a number underneath it. By moving the slider (below the box), you will change the number appearing on the computer screen behind the palette to one of these numbers corresponding to a grayscale chip value. Try to find the grayscale value that most closely matches the target patch. When you have found the closest match, press the red button to lock in your match and move onto the next trial. You are encouraged to look back and forth between the computer display and the palette several times before locking in your match; however, if you do, please be sure to put your head in the chinrest when looking at the stimuli, to ensure proper 3d perception. 

There are three special values on the slider that do not appear on the palette. If you shift the slider all the way to the right, you will see "Lighter than 9.5, but still a surface", and further right from that is "Glowing". If you think that the square target patch looks lighter than the palette chip corresponding to 9.5, but that the target patch does not appear to be glowing as though it were a light itself, pick the former. If, however, the target patch appears to be self-luminous, pick "Glowing". If you shift the slider all the way to the left, that corresponds to "Darker than 0.5". If you think the patch looks darker than the darkest palette chip corresponding to 0.5, pick this option. 

There are a total of 108 trials. The program will ask you to stop to take a break every 36 trials, or every third of the way. Please take this opportunity to rest your eyes for a few minutes--the experiment is taxing! 

If you have any questions at any point, please feel free to stop and get the experimenter. There is no time limit, so please try to make the most accurate match you can. 

Thanks!