What is "fusion"?

I'm writing this entry to describe my experience with "fusion" in vision therapy. I'm putting "fusion" in quotes, because I'm still not quite sure if what I am experiencing is fusion, or even what the definition of fusion really is. I know that, basically, fusion means two eyes making one picture. But what I've seen and noticed seems much more complex, and involves brain processes that I can't even begin to understand. In any case, this is what I have noticed about fusion so far...

First, I have noticed that fusion is not just one process. There seem to be several "types" of fusion that I have come across, and even within these "types", lines get blurred and things get murky. These types may even exists on a continuum. However, I will try my best to explain what I have experienced. Here are the three types of fusion that I have come up with:

1. Cut and paste
 This is the easiest kind of fusion for me. The images from each eye are selectively cut and pasted together into one image through some brain photoshoppery. An example of this would be the anti-suppression playing cards that I love so much.

When viewed through red/green(blue) glasses, these are the images that the brain must combine:

How does the brain do this? In my subjective experience, it feels as if my visual system is using scissors and glue to make a sort of collage.

Of course, it doesn't look like that. But it feels as if that's the process that my brain is going through - choosing the important elements from each eye, and deciding which to use in the final "collage." If the brain did not go through such a process of defining importance and cherry picking input, then what would stop the brain from making an image such as this?

The brain would not make the above picture, and one would never see the cards all blank like that. I dare you to try! The brain looks for meaningful input, and assembles everything together accordingly. That is why, when making anti-suppression activities, I am always writing letters on everything. I have learned from the playing cards that the brain cannot ignore letters.

For me, this type of fusion becomes more difficult as finer and more precise "brain cuts" and "brain pastes" are required. For example, fuse - by convergence or divergence - the image below:

What you should see is something like this:

This is quite hard for me to do, and I believe I know the reason why. Look at all of the places where the lines are in conflict (in pink). This would require some very creative cutting and pasting.

In fact, this comes close to requiring the brain to create a completely new image (rather than a collage), which brings me to the next kind of fusion.

2. Transmutation
In this type of fusion, something new is created that neither eye can see alone. This is not a composite of two images, as is the case with cut and paste fusion. Two images are combined in such a way that they create a new, unique third image.This is certainly not a collage. It's a new painting!

An example would be the "luster" effect. By convergence or divergence, fuse the two images below:

What you should see is one grid in the middle, with the red square and the yellow square magically transmuted into a new color. This new color was not perceived by either eye, it was created in the brain. (I imagine it will be glowing like it's fresh out of a nuclear reactor.)

This type of fusion is exceedingly difficult for me, and I'm not sure that I have properly achieved it. When I try to do luster activities, I tend to get flashing, alternating between colors, rather than the creation of a new color. I also imagine that stereoscopic vision requires a great deal of transmutational fusion, and thus it is very important that I get better at it! I can't be satisfied with merely cutting and pasting; my brain needs to learn how to blend and create.

3. Stereopsis
What happens here? I'll let you know when I see it. I've heard that salads, tomatoes, horse skeletons, steering wheels, and coat sleeves all start jumping out to say hello. It sounds pretty awesome.