Seeing the Full Picture

Part II: The flaws in our design

Human eyesight is a pretty poor servant. We don’t just “not see all that well”. We see badly in low light and bright light… and we see badly in two very different ways.

One of them messes up our vision. The other messes up our whole nervous system.

Like a camera, our eyes are designed with a lens of their own which lets in light and then refracts it onto a surface. In an old-fashioned camera, that surface was the film. In our eyes, it is our retinas.

That surface is there to first receive information from what is being seen and then do something useful with the information.

To enable the first part, gather the information, our retinas are packed with little receptors called “rods” and “cones” that register light and color. And once they have, to make that information useful, they ship it up to our brains.

Rods are the structures in our eyes that detect light. Cones are the ones that detect color.

Rods are concentrated in the outer part of the retina. Cones are concentrated in the middle.

The makes sense if you think about it. When do our pupils dilate? In low light. Our pupils “get bigger” to allow more light – more information - to get through the lens and hit the retina. Since light only hits the outer parts of the retina when pupils dilate (because it’s dark) that part of the retina is loooooaded with the structures sensitive to light.

Conversely, since humans really only needed to see whether a berry was ripe or rotten during the day when there was enough light, cones are concentrated in the part of the retina that gets light when pupils aren’t dilated – because it is light out.

It’s like an old-fashioned snow cone. To make one, you start with a paper cone of white ice and then pour a colored syrup right on top which then bleeds outwards and down to color the whole thing… That bite right on top was always better than the edges because it got the most color. The syrup. Remember the snow cone metaphor and you’ll get the whole rods and cones thing. Color vision is concentrated in the middle. Light vision is concentrated outside of it.

That little design creates two completely different vision problems…

When it is too bright and our little camera shutter closes to let in less light, it hits the middle of the retina where our eyes are worst at detecting degrees of light.

Imagine look at someone when the sun is directly behind them. Instead of seeing a colorful scene because the light is hitting the cones just fines, you instead see too little gradation of light. You see only the silhouette of the person contrasted against the bright sun… and you can’t see any more detail than that unless you shade your eyes to reduce the light and get more of your retina involved.

In really bright light, we see things as artificially black or white. We don’t see shades.

In low light, on the other hand, our little camera lens does the opposite. It opens wide to let more light hit the part of the eye better at processing it. The perimeter.

(If you want to test this out, go outside on a clear night. Out of your peripheral vision, find a dim star… and then try to look directly at it. It will… disappear. You won’t see it anymore because the center of your retina isn’t good at handling light. Your peripheral vision can see light your direct vision cannot.)

It’s kind of cool actually. But it reflects the fact that our vision is actually designed to suck in the dark generally. We can’t really see color at all and can only see dim objects peripherally.

In low light, we see only the shape of things.

That particular flaw is much worse than it’s bright-light cousin. It fucks us up on the regular.

To explain, we have to go back to life 5,000 years ago but I swear, it will be very brief.

Back when humankind operated mainly in daylight, the biggest threats to our survival were bumps in the night. Predators tended to operate under low light or darkness. While we might not have been able to see well at noon on the brightest day of summer, there wasn’t much that was going to saunter out into the field where we were picking berries and eat us.

At night though, stuff we couldn’t see well could, in fact, be angling to make a meal of us. Or we could walk off a cliff or fall in a river or otherwise self-Darwin.

Since people who have fallen off a cliff in the dark tend to have few children thereafter, natural selection did its thing and voila! Humans developed a lightning-quick danger response that has a hair trigger in darkness but not at noon.

In our brains, there’s a little structure that functions like a security guard sitting at a row of monitors. Our eyes stream a live feed… The security guard gets it in real-time. The rest of our brain get it on a slight delay. When the security guard sees something that could even possibly be dangerous to us, it pulls an alarm so crazy-fast, it goes off before the rest of our brain has even gotten the frames.

Ever been somewhere dark – on the street, in your own home, wherever - and been suddenly startled by the shape of something? A person that turned out to actually be a mannequin, an object that looked like something else, something moving...

Well, that’s your vision sending only a grainy, dim file in the dark and your brain having to use it to keep you from being eaten.

Your vision saw a shape without contrast or detail. Your brain hit “red alert” based on the shape.

I was alone in a dark office late one night. Shut down my computer and started walking through the dim halls. Saw a person in the darkness and almost jumped clear out of my shoes. OMG. It scared the absolute bejesus out of me. It was a cardboard cutout. And I had known it was there. I had seen it several times that day. In low light though, where we see shapes without color or nuance, our brains hit red alert before we have even had a chance to think. Literally, our entire fight-or-flight system goes Defcon 5 in a millisecond before we even realize that Paul in the trade show room left the damn exhibits in the hallway.

And that, at long last, brings me around to the point of all of this:

It seems to me that the way our vision works well explains why things are so polarized at the moment. We are all suffering from flawed vision of one kind or the other because all humans have flawed vision. The problem is that we neither know that nor understand how it affects us. And worse, those flaws are being exploited.

And that is the topic of the final installment here, Part III