Tuesday, April 23, 2013
The Eyes Have It
The difference between “looking” and “seeing”
At the same time that we're recognizing the target-like structure of our vision, we should also recognize that it's very possible to "look" but not "see," even though we think we're concentrating on the bull's-eye. This is the super-common tendency to look through the windshield and think we're seeing what's happening out there but we really aren't. Our eyes are seeing a generalized picture of the scene that's in the windshield, but we aren't really focused on any of the small details that would be giving us vital information IF we saw them. Which we often don't.
The tendency to "look" but not "see" affects us in two different areas: the first is when looking over the nose and judging the nose's motion against the background, as in takeoff and landing, or while making turns. The other is when looking over the nose (and out the side windows) while trying to see what's out there, collision avoidance being the most critical of those.
Even though surveying ground references, as when on a cross-country, fits into this conversation on visual acuity, that's a form of "looking" in that pilots innately understand the difference between "looking" and "seeing" and, without realizing it, use their eyes differently.
It's a given that if the eyes aren't focused on a point, i.e., if they aren't picking out something specific, they get lazy and tend to focus short. This is apparently what happens, when using a casual, constantly moving scan while looking for traffic in a featureless sky. According to the FAA, this focusing-short phenomenon is called "eye myopia." In slowly moving our eyes across the sky, as most of us do, we're not giving the eyes anything to focus on, so they've focused short, and we're not likely to see another airplane even if it's in plain sight. This doesn't happen when looking at the ground checking for checkpoints because we're asking our eyes to focus on and identify features of the landscape. They're constantly picking out new features, so they're continually changing focus and we're basically ignoring our peripheral vision even though it's there. It's not applicable, so we don't use it.
When scanning for traffic, the FAA tells us that our eyes work better if we separate the sky into roughly 10-degree sections. We should then spend 10 or 15 seconds (according to them: seems like a long time to us) examining each section before moving on to the next one. The theory behind this kind of visual scanning is that by concentrating on small segments we've given our eyes the task of focusing on that specific section so they focus much better. We also can apply the same concept to other parts of the flight. Which brings us back to taking off and landing, making turns and the difference between "looking" and "seeing."
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