Sunday, January 21, 2007

Artifacts of Vision by Louis Evan Palmer

The greater the level of interaction we find we have with what we "see", the greater the question is as to what we do not "see" and how and why we "see" the way we do.

The eye was the thing that most amazed Charles Darwin on his epoch-making sea journey and, indeed, this amazing organ is the gateway for some 80% of an average human's perception. However, as magnificient as it is, the eye is only part of the visual cognition process. Additionally, there are the optic nerves, one per eye, and the brain itself. There is also a nebulous thing called attention which calls forth other phenomena like the "will" and emotions and beliefs that colour, even shape, what we see.

We "know" what we see because it's been subtlely (and not-so-subtlety) explained to us until our agreement is effortless and unquestioned. Expectation plays a huge role in what we see; it does help us to process more quickly and more effectively, however, it can be more what we (think we) should see than what we consciously & unconsciously see.

The way vision is constructed, or our current understanding of it, is probably not what most of us thought. The understanding is still under construction but various surprising discoveries have been made over the last few centuries especially since the second world war.

For example, each of our eyes has an optic nerve at the back of the eye. This results in a blind spot where the optic nerve exits the eye on its way to the brain - there are no cones or rods. We don't see this hole in our vision for two reasons: firstly, the optic nerve is not in the same position in both eyes so the blind spot of one eye is covered by the other eye; secondly, even if using a single eye, our brain (or our brain-mind) fills in the hole.

Or, we blink every 4 to 6 seconds; it's very quick between 100-150 milliseconds. Why don't we see darkness at that moment? Why doesn't our vision appear as a series of snapshots? One theory was that a phenomenon called "persistence of vision" came into play - an afterimage stays on the retina long enough for the eye to blink and see again so we would in effect be seeing snapshots but not noticing it. A more recent theory is that part of the brain turns off during the eye blink and this is the part that would notice the darkness - so if we don't notice it's dark then as far as our vision goes, it isn't.

Even if "persistence of vision" doesn't seem to play a part regarding uninterrupted vision during eye blinking, it does allow us to see many flashing or discontinuous lights (and things illuminated by light) as continuous. If the light or image is sent at the correct speeds, our brain will intergrate them, it will make the discrete continuous . After light has hit the retina, chemical processes take over. A period of time, called integration time, is needed to process the image. More integration time is needed in low light.

A motion picture runs at 24 frames per second but by shuttering each frame 3 times, the flash rate becomes 72 times per second. That speed is faster than our brain can integrate so we do not see any flicker. Same thing happens with computer monitors which flash at some 75 times a second. Same thing happens with many regular lights especially fluorescent lights.

Another interesting vision-related phenomenon has to do with what light an average person can see. In our eyes, cones, which see colour, are able to detect within certain frequency ranges only. Rods detect lower levels of light. If a coloured light is dimmed, we will see it and its colour until it reaches the threshold for its frequency to be detected by our eyes' cones and then it will be seen but as a grey light - no colour; unless it's a red light, in which case, when it hits the threshold, the red light will disappear to our vision.

We have another blind spot which occurs at night. The center of our visual field is called the fovea - it contains only cones, no rods at all. Therefore, if an object is small enough to fit into that visual center and the light is low enough, we will not see it.

Many of the above visual artifacts have a strong physical component but there are other visual cognition phenomena that have much more of a mental aspect. One phenomenon is called "change blindess" and refers to how people can fail to notice significant changes from one scene to the next. Another phenomenon focuses on the role that attention plays in what you see but, more dramatically, what you do not see.


For the beckman video, for your first viewing, your task is to count how many times the players with white shirts pass the basketball among themselves, only focus on them. Then watch the video again.

This does not touch on "vision" when we dream, reports of remote viewing or OBEs (out-of-body-experiences).

Artifacts of Vision, The Way It Can Be, Louis Evan Palmer,
Copyright Louis Evan Palmer 

He lives in Ontario Canada. His short stories have been published in numerous publications.


No comments: