Background

The news is not all bad for dichromats, though. In fact, it is surprising there are so many of them given all of the difficulties we have outlined in this chapter. Maybe, they have some sort of advantage that helps them evolutionarily. Morgan, Adams, and Mollon (1992) discovered that dichromats can see through some forms of color camouflage that completely mask objects to color trichromats. There had been anecdotes since World War II about color deficient people seeing objects hidden by camouflage, but this study was the first to demonstrate this ability in the lab. Participants had to locate a square of horizontal rectangles in a field of vertical rectangles. If the dots are all one color (see below on the left), the square is easy to find for all of us. When the figure is camouflaged with a random array of red and green dots (see below on the right), trichromats perform practically at chance whereas dichromats still perform quite well.

Use this activity to explore this experiment. First, try it yourself. If you are trichromat, see if using the camouflage is harder to do the task than without. If you are a form of red-green color deficient, see how you do with the camouflage.

Instructions

Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab

Settings

Below is a list of the ways that you can alter the illustration. The settings include the following:

Start: start a trial. Look at the cross in the middle of the screen. The grid area will be shown with the smaller box of horizontal grid elements with in it. After the stimulus has been removed, you will be asked in which of the four quadrants the smaller square was visible.
Use Mask: if no, the stimulus will be all one color, if yes, the stimlus will randomly draw some of the elements in a second color as a camouflage color.
Horizontal/Vertical Difference of Elements: To make elements either vertical for the main part of the grid or horizontal to make up the target, this value is how different are the two directions of the elements. The bigger the difference, the easier it is to find the target.
Duration (ms): how long with the stimulus be presented, in milleseconds.
Delay: Time between the end of the fixation mark and the stimulus, in milleseconds.
Stimulus Size: how big will the stimulus be relative to the height of the drawing area.
Element Color: The color to be used when no mask is present, will also be used in the camouflage, masking, condition.
Mask Color: the second color that will be the color added during masking to make the camouflage.
Background Level: the type of gray for the background. It is best if the backgrouns is about the same brightness as your stimulus.

Reset

Pressing this button restores the settings to their default values.

Try these settings explore our ability to see through color camouflage.


Use Mask: Yes No

Element Color	Mask Color

Stare at the cross in the middle of the screen. To start a trial press the stimulus area or Start button. A grid of small blocks will be shown. In one quadrant, there will also be blocks that are horizontally oriented. After the stimulus is removed you will be asked where the small block was. After you do a few trials, set the stimulus to Use Mask which will randomly change some of the blocks to the mask color. Now see how you do. What Morgan, Adams, and Mollon (1992) discovered was that people with a red/green color deficiency were much better able to find the horizontal blocks when the mask was on than the more common trichromats.

Proceed to Quiz