Brian Carter

So, my first post so long ago was on the fovea, even if I didn’t refer to it as that. I ended it with “let’s see what else we can come up with!”. And so, just recently I did.It’s a hypothesis of the vaguest sort, and I expected to be dismissed or disproved by everybody I discussed it with…but my visual perception professor didn’t dismiss it, nor has anybody else. Still, I offer it up with this caveat: I might be wrong.I was reading my VisPerception course packet and they went over all of the well-known optical illusions. As I was experiencing them, I was asking myself what everybody does when viewing illusions: “How can I be experiencing something so wrong?” It is pretty rare we get confronted with just how easily our perceptions are fooled.I tried looking at this illusion with the knowledge of the fovea: that everything we see is a tiny piece of sharpness in the center of a blur and I realized something.We don’t see it like that. We see it like this.And that makes all the difference.The other line is actually just a rough approximation of the line that’s actually there. We can’t see them both at the same time. And while our eyes saccade from one to the other, our peripheral brain is constastly swapping out what it thinks about the other…based on a rough guess of a blurry image.A hopfully clear description of the entire process:We look at one end of one of the lines, the left end of the top line like in my fovea simulation. The blurry ends we have of the other line is much further away from the only landmarks we have, the diagonal lines. Our brain tags it as “a longer line”. If we then move our eyes over to an end of the lower line, we’ll notice that the inverse is true: the blurry line is “shorter”. Our brain is confident because it got many rounds of confirmation.Try this. Look between the two horizontal lines so that all the edges are in your peripheral. You won’t be as fooled.Like I said, the fact that my explanation seems “simple” and “easy” compared to the explanation in the Visual Perception course book (which said that the diagonal lines became depth cues and we viewed it with 3d and perspective in mind.) makes me feel like a bit of a crackpot. Still, I think looking at the world with the knowledge you have a fovea is a real eye-opener.That’s not a pun because it’s used literally.

Try focusing on one word on this page and without moving your eyes see how many other words you can read. Not very many, right?

The Science of It

The rods & cones in our eyes are not distributed evenly. They are much denser at the center and therefore our vision is clear only at this center. Everywhere else, it’s foggy and undefined. Why don’t we notice this? Because whenever we shift our eyes to look at a spot that was previously foggy…that spot becomes the center and we can see it clearly.

What does this mean?

Well, it means we don’t see a lot of what we think we see. We are constantly filling in data about everything that’s not right in the center of our eyeballs. We are sensitive to movement in our peripheral. (With good reason – how often do stalking predators walk right into our gaze?) It also means that we could consider peripheral vision almost a sixth sense.

Try this: Stare straight ahead. Raise your hand up so it’s level with the side of your head. Wiggle your finger. Slowly move your hand around to your face. Do you notice how you can tell when it’s within your line of vision…but you can’t say anything else about it other than: it’s there? Close one eye, then the other. The eye closest to your wiggling finger sees it, while the other eye doesn’t at all and since your vision is a composite of both eyes, you (vaguely) see it and (vaguely) don’t see it at the same time. (“Schrodinger’s finger”, if you will.)

Practical Applications?

The first and most obvious use (to me, anyway) is to use whitespace to calm the eye. Most applicable to graphic design but useful elsewhere as well. If you want somebody to concentrate on something…empty all the space around it. The empty space will attract their vision anyway.

Perhaps this is why “trapped white space” is so bad…enough white space to surround something but not enough to clear our peripheral so our eye darts back and forth “hey what’s that thing over there?”.)

Seeing movies on large screens is also an exercise in peripheral vision. Your eyes move around the screen like they would around a landscape, settling on details here and there. This allows us to “actively watch” a movie.Peripheral vision also allows directors to fool us. Take a look at this shot from Jaws with some simple Photoshopping to approximate what it looks like to a first time viewer, focusing on Brody’s eye or mouth. Notice how the top row of shark teeth intersects Brody’s eye and the bottom intersects his mouth? If our ancestors weren’t hardwired to freak out at that image, we wouldn’t be here.Horror movies are filled with this sort of stuff. I can think of several others off the top of my head. (The shark crashing into Hooper in the cage in Jaws, the Alien swooping down behind Brett in Alien, the alien grabbing Dietrich and so on, and so on)Yeah, it can startle us, but lets think less about the techniques that have been used for it and what we can do in the future with it.