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 target patches. You can think of "lightness" as "what color paint the patch 
is coated with". In some conditions, you will make judgments about the angular 
orientation of various surfaces in the display. 
 
On each trial, you will see two squares ("contexts"), each consisting of a random 
assortment of grayscale rectangles. In two different conditions, these two contexts 
can be at one of three angles relative to each other. You will also see a patch near the 
center of the display. The patch will be oriented at a number of different angles. This 
patch is called the "target patch". 
 
In some conditions, you will make matches to the target patch lightness. To indicate 
your judgment about the lightness of the target patch, you will use the palette to 
your right. Notice how each grayscale chip has a number underneath it. By moving 
the slider (located below the wooden box), you will change the number appearing 
on the computer screen behind the palette. The number will correspond to one of 
these numbers on the grayscale chip palette. 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 the proper 
perception of the stimuli. Sometimes, you will view the stimuli with both eyes; other 
times, you will view the stimuli with just one eye. A piece of felt will cover one of the 
eye holes when you view the stimuli with one eye. 
 
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 the option "Glowing". Slightly to 
the left of that point is the option "Lighter than 9.5, but still a surface". If you think 
that the target patch appears to be self-luminous, pick the former. If you think that 
the target patch looks lighter than the palette chip corresponding to 9.5, but that it 
does not yet appear to be glowing as though it were a light itself, pick the latter. If 
you shift the slider all the way to the left, you will see the option "Darker than 0.5". 
Pick this option if you think the patch looks darker than the darkest palette chip 
corresponding to 0.5. 
 
In some other conditions, you will make matches to the orientation of various 
surfaces in the display. To indicate your judgment about the orientation of the 
surfaces, you will use the game pad and the display in the booth to your right. A 
white line will appear in a green circle. By pressing up or down on the game pad, 
you will rotate the line until it matches the orientation of the surface in question. 
You will then lock in the match by pressing a button on the game pad. Note that the 
line represents a side view of the surface, viewed from the left. 
 
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!