Dyslexia, Visual Illusions, and Binocular Rivalry???

(binoculars with swirl image in optics, suggesting effects of a visual illusion)

For those who saw my last post, What Visual Illusions + Contrast can teach us about Reading Disorders, this is a second step into what optical illusions and the visual cortex (the part of our brain that is the true source of most optical illusions) can teach us about reading disorders.

In this post, I’m going to talk about binocular rivalry, a phenomenon of binocular vision (think monkey/human eyes versus fish eyes). It turns out that you can force your eyes into another form of optical illusion with competing images.

Okay, let me help you catch up without forcing you to read a Neuroscience journal.

“Binocular Rivalry” is like Sibling Rivalry, only it’s your eyes.

Remember your obnoxious kid sister? You know, that constant infighting of “who-tagged-who-first” that goes on in childhood? Turns out, your eyes are capable the same thing! They can get competitive about who is right and who is wrong…but it takes a pair of “wacky binoculars” to get the fight going for people with normal vision.

Wacky Binoculars = Visual Fight

Here’s what the neuroscientists did to make your eyes “fight each other”. They gave the subject a set of special binoculars that, instead of offering telescopic vision, offered 2 very different static images for each eye.

Here’s an example of what the left eye might see…vertical lines.

(vertical striped image)

And this image on the right side…horizontal lines.

(horizontal striped image)

Ready, Set, Fight!

So your left and your right eye are getting significantly different data. Just like a persistent visual illusion cannot be rationally resolved, neither can the disparate data in each eye. So they get into an argument, just like two bratty kids. At first, they flip back and forth.

Not sure about the exact timing of how fast it switches, but your brain basically decides to jump back and forth between the two images for a little while, fighting each other for dominance…

(simulation of visual cortex switching between vertical and horizontal images)

And then, in an attempt for a “Visual Compromise”…this optical illusion occurs…

(bizarre image resulting from visual cortex’s attempt to merge unlike images)

…and then they cycle right back to fighting for dominance until you take off the wacky binoculars and the twins make up.

Why does this binocular rivalry matter?

Because it’s the desperate attempt of your visual cortex to resolve two completely different images. Your brain is trying so hard to find a happy medium that it “invents” a compromised image to satisfy the patterns which, let’s be honest, looks like a 3-year-old’s attempts at finger-painting.

Let’s maintain the premise I suggested in the first blog, that a person with Dyslexia or another reading disorder is more susceptible to optical illusions. Would it not be possible that the strategies that result in the “visual compromise” state you just saw in binocular rivalry, might be related?

Just like that “visual compromise” we experience when two images cannot be correctly resolved, might it be possible that reading disorders are “over-tuned” to try to resolve/compromise differences…perhaps even when there isn’t actually a problem?

Let’s test some ideas out on a real Dyslexic…

A recent friend I made, we’ll call him “Albert”, is Dyslexic and offered to help me review the possible relationships from a Dyslexic’s point of view. We tried many things, but one of the common problems that Dyslexics experience stuck out immediately.

The double-letter illusion.

If you know anything about Dyslexia, you’ll be aware that one of the more common issues they can experience is double-letter illusions.

Albert experiences visual illusions after a few minutes of reading when he reads words like…

• balloon
• letter
• barrage
• allied
• artillery

In these cases, Albert described the visual illusion appears to be trying to “compress the word”, at the point of the double letter. Based on Albert’s description, here’s a sequence simulating of what one of those experiences might be like…

As you can see, the “r” characters are gravitating towards each other, trying to resolve something…but what? Is it a binocular rivalry issue? Where the eye sees two patterns in a sequence and Albert’s visual cortex assumes that it’s actually just one?

This is quite possible.

Of course, if binocular rivalry were the sole source of the problem, we would be able to cover up one eye and that would be the end of the problem, wouldn’t it?

It could also be that this optical illusion is happening later in the “visual processing” and has an inherent assumption of binocular rivalry, whether you are seeing with two eyes or one. Then, it wouldn’t matter if you covered one eye or not.

(sigh)

Yes, I admit, this is pure speculation.

As was pointed out to me by a neuroscientist, the mechanisms behind binocular rivalry are still not really understood. But before you dismiss the possibility of a relationship, let me show you another optical illusion that Albert experienced — one that I found extremely intriguing.

Illusion by indenting???

After attempting several other manipulations, I decided to throw Albert a “curveball” of sorts, by indenting every other line of paragraphs. This is what it looked like…

(image of alternative indenting of paragraph)

Albert immediately noticed an optical illusion that was “pushing out the indented lines to the left” to match the non-indented text. Just like the rr pattern in barrage was causing a partial collapse of the word.

It seems highly likely that Albert’s visual cortex was trying to “force a fit” that simply didn’t exist in both cases and offering a visual illusion which it perceived as a “compromise solution” when it couldn’t resolve it.

Whether binocular rivalry as an individual pattern is related to Dyslexia or other reading disorders, I cannot say. Honestly, I haven’t done enough research to substantiate such an idea — but the simple fact that binocular rivalry can result in a “visual compromise state” bears a lot of similarity to the “visual compromise” that exists in Albert’s optical illusions.

Perhaps the visual illusion he experiences is actually an attempt by his brain to “compromise” when it sees an incomplete pattern that it believes is supposed to be resolved.

So, what does this mean, from a design perspective?

Well, basically — we should be figuring out what “triggers” exist for optical illusions and then be designing a means to either suppress them or kill them altogether.

Contrast reduction, as I pointed out in my last article, is a great way to approach the problem, but it isn’t the only means or the only thing we should consider.

What’s next? Manipulating your own visual illusions!

In my next post, I will be providing some means to tweak your own visual illusions — and practical examples of how we can partially or completely disable optical illusions in other ways other than contrast, my original post on this topic.

If you want to follow me on Twitter — I will be announcing the release of the blog post there.

Thanks for reading!