From: David Rudiak <drudiak.nul> Date: Sat, 21 Apr 2012 15:52:00 -0700 Archived: Sun, 22 Apr 2012 08:30:26 -0400 Subject: Re: Ufology And Psychiatry - Summary >From: Cathy Reason <Cathym.nul> >To: UFO UpDates - Toronto <post.nul> >Date: Sat, 21 Apr 2012 11:42:17 +0100 >Subject: Re: Ufology And Psychiatry - Summary >>From: William Treurniet <wtreurniet.nul> >>To: post.nul >>Date: Thu, 19 Apr 2012 14:05:17 -0400 >>Subject: Re: Ufology And Psychiatry - Summary ><snip> >>The comment that the unreliability of human perception is an >>assumption is demonstrably wrong given the oft-demonstrated >>variability in relevant experimental data. >We can see how this sort of circular reasoning operates in the >case of visual illusions. >To the vision researcher, these offer an opportunity to examine >the mechanisms by which the brain extracts information from the >visual world. By constructing experimental artifacts, one can >test hypotheses based on how the visual system behaves in highly >novel and constrained situations. >Psychologists on the other hand proceed from the premise that >all human perception is unreliable. The purpose of all >experiments is then to provide an ever-lengthening list of >examples of unreliable perception. It matters not that these >examples are largely artifacts - the premise dictates the >conclusion. Dead on Cathy! Visual illusions are actually quite rare in a natural environment, otherwise we would be suffering from them all the time. Most illusions you see in a book on human perception are the result of highly artificial situations that one usually would not encounter in normal life, usually a very simplified, geometric drawing with all sorts of normal cues stripped out that would have prevented the illusion from arising in the first place. One such example is spoke-like lines radiating out of a central point, with two straight parallel lines drawn through them. The two lines appear to be arced instead of straight. Interestingly, the illusion can be somewhat suppressed by interpreting the spokes as receding into the distance toward the vanishing point. To a vision researcher, this tells us something about the processing of straight lines in the brain (also a little about depth perception). E.g., one explanation is that neurons responding to different orientations of lines inhibit one another in the brain, resulting in acute angles appearing a little larger than they geometrically are and obtuse angles a little smaller. If you apply that to the above illusory drawing, the local small distortions of angles will cause the straight lines to arc a little bit when the brain interprets the overall shape of the lines. But in a normal situation, the mechanism helps the brain distinguish orientations of edges and sharpens up differences. In computer image processing, it is well known that filters applied to a scene can help bring out certain features, but at the expense of creating artifacts. The brain is no different. Evolution has led to the brain applying various neural filters to the image that assist us in representing the scene and ultimately interpreting it. These sometimes create illusions, but usually one has to work pretty hard to mislead the perceptual system. Interpretation, which is an end-product of raw perception, can also be faulty, but there is nothing inherently true in an image, which can have multiple ambiguous interpretations, also raw fodder for generating illusions for those perceptual studies. E.g., an old classic illusion is the Necker cube, nothing more than a black and white line drawing of a cube with "front" and "back" faces the same size. What is "front" and what is "back" is ambiguous and can and will flip back and forth. And you can, of course, not interpret it as a 3D cube, but as a flat line drawing of two squares connected by slanted diagonals, or just a bunch of intersecting lines. There really is no inherent "cube" there. We tend to prefer to interpret the drawing as a solid. A real 3D cube, particularly one made only of edges and not solid, can also be mentally flipped, but this is more difficult, and that can result in more illusions. The front and back surfaces are no longer the same size, also in different focal planes. Note that in normal viewing with two eyes, the following illusions will usually not arise, because our binocular vision and depth perception will prevent the illusions from arising in the first place, again our perceptual system usually being quite accurate and robust. It is usually only in an artificial laboratory setting with multiple cues stripped out that the illusions will arise. Thus, subjects need to view the scene with one eye, not two. In the normal situation, it looks like a proper cube with everything focused right, but when you mentally flip it in becomes a trapezoidal solid, where the focus of the front and back also do not appear to be consistent. Thus already there is an additional cue that something is not quite right. More inconsistencies arise when you rotate the solid in your hand. As a cube, it rotates consistent with another part of your brain's understanding of what direction you are rotating it in, but reversed it appears to paradoxically rotate in the opposite direction. This illustrates how the visual brain areas are communicating with one another to keep the visual interpretation consistent, but this conflicts with the sensory and motor ones. Again, we quickly smell a rat that something is not right with how we are seeing things. Another striking illusion with a rotating wire cube is putting a straight stick through it. Viewed as a normal rotating cube, the stick remains in rigid relationship to the cube, following the rotation of the cube and we properly see it as a straight stick going through two surfaces. But when the brain mentally flips the depth and it becomes the reverse-rotating trapezoidal solid, the stick no longer remains straight but seems to rapidly contort into all sorts of extreme shapes. This is again the visual brain trying to keep all elements consistent with one another. The stick shape has to morph and seem to twist to maintain its proper geometric relationship with the illusory trapezoidal solid. But again, the situation is pretty artificial. To the vision researcher, this is another example of how the various visual brain interpretation mechanisms work hand-in-hand to maintain a consistent interpretation of the entire scene. But a psychologist (or a debunker) might interpret this as another example of how unreliable human perception is. For fun, you can also try to flip a solid cube, like your Rubik's cube, and other interesting illusions arise, such as surfaces that seem to have no depth and the colors now look like stained glass illuminated from behind. To get it to work, you have to concentrate a lot and stare a long time until your nervous system begins to fatigue and the alternate, non- fatigued, but less favorable interpretation can occur, again not a normal situation. David Rudiak Listen to 'Strange Days... Indeed' - The PodCast At: http://www.virtuallystrange.net/ufo/sdi/program/ These contents above are copyright of the author and UFO UpDates - Toronto. They may not be reproduced without the express permission of both parties and are intended for educational use only.
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