Before getting into the specific physical characteristics of identification, I think it is important to briefly discuss the process of perception. Identification of a snake's species through "real time" comparison with pictures of known specimens is fairly straight forward. Identification of a snake from our memory is much, much harder. A familiar adage says that "Seeing is believing." However, this is gross simplification of the process of perception. A more correct statement would be that "We see what we believe."

There are two principal parts to the process of human visual perception. The first is the physical activity of receiving visual stimulation. Let us call this process "camera sight." This is the process of absorbing light through the eye and converting it into neural signals in the retina. This process can be compared to that of a camera receiving light through the lens and converting it into a chemical image on the film. Camera sight is a purely physical process and, as such, is unique and repeatable. Using identical cameras with the same type film to take simultaneous pictures of a object from essentially the same angle and distance, will yield essentially identical pictures. If human vision consisted only of camera sight, then barring major eye diseases, we would all see the same thing when viewing the same scene. To a great extent this is true of human sight, but only for unconscious or reactive processes. We often respond to visual signals without conscious recognition of these signals. Most visual information is of this unconscious nature. For example, as a person walks down a crowded sidewalk, he constantly scans the pathway and makes unconscious, reactive corrections to his movements in order to avoid stumbling or bumping into other people.

Snake species identification requires "conscious vision." A person may unconsciously react to a snake in his pathway. He then focuses his vision on the snake and receives much more detailed camera sight of the snake. However, he probably still will not consciously see very much more detail about the snake! Why not? In order to see a snake, or any other object, in our conscious minds we must make correlations between what our camera sight is providing us and the knowledge that we already have stored in our minds. For example, we may first correlate the sight of a snake with our concept of a stick. Then we may correlate the stick with a measurement such as a yardstick; and then perhaps with a flexible, stick-like object such as a rope. Then we may associate the rope with a general color, such as black, brown, or red. These type correlations cascade through our knowledge base. With each correlation, we register a conscious image of the snake in greater detail. However, at some point our knowledge base ends and the image of the snake becomes fixed in our memory. The accuracy of our remembered snake is dependent upon quality and extent of our previous knowledge of what snakes look like.

When consciously perceiving an image, we do not always have to start with such an elemental correlation as that of a snake to a stick. Before having ever seen a real snake, most everyone has been provided some conscious images of snakes through drawings, books, TV and films. We probably have an image of a giant snake, such as a Python, Boa, or Anaconda; the venomous Cobra with its raised, fan-shaped head; and the Rattlesnake coiled and ready strike. I like to call these previous images visual "models." Once our minds tell us we are seeing a snake, we can then efficiently bypass many lesser correlations and jump to one of our snake models. We can then say the snake is like a cobra but without a hood. And so on, and so on.

The more snake models we have in our minds, the more details of the snake's appearance we are able to consciously see. Also, the more quickly and efficiently we will be able to identify its species. With snakes, being able to quickly recognize details of its appearance is very important since we usually do not have long to view them before they disappear. Persons who have caught, handled, and/or studied snakes can make quick, accurate determinations of species principally because they already know, that is have models of, what they are seeing.

I hope that it is now clear why I thought it would be useful to delve briefly into the theory of visual perception. First, it is important for any observer to recognize that what he remembers as having seen may not be complete or accurate, no matter how vivid the memory may be. Secondly, the accuracy of identification is greatly enhanced through prior study.