Please
read chapter 6.
After reading chapter 6, please respond to the following questions:
What were three things from the chapter that you found interesting? Why were they interesting to you? Which one thing did you find the least interesting? Why? What did you read in the chapter that you think will be most useful to in understanding Sensation & Perception? Finally indicate two topics or concepts that you might like more information about.
Note:
Keep in mind that there are no scheduled exams. When you make you posts
make sure they are of sufficient caliber that the could be used as
notes in a test - since the posts are what we are doing in lieu of an
exam. Be sure to use the terms and
terminology in your posts.
I enjoyed reading chapter 6, and found many things intriguing but found a few concepts particularly interesting. I liked learning about binocular summation because I think it’s important to understand the differences between visual fields of varying species. The textbook gave the example of why it’s hard to sneak up on a rabbit. A rabbit’s visual field is like a planetarium dome, whereas, a human’s visual field is like a windshield. The rabbit’s visual field extends 360 degrees and they can even see straight up above them and down to the ground on the left and right, but not underneath their nose and mouth. In contrast, a human’s visual field is only about 190 degrees from left to right in front of them. Of those 190 degrees, both eyes cover about 110 degrees. Unlike rabbits, humans’ visuals fields only extend 60 degrees up and 80 degrees down. These differences are thought to be a result of evolution, allowing predators (humans) to see small, quick animals and objects in front of them to catch and eat. The rabbits along with other prey animals have the dome-shaped visual fields to avoid getting caught by the predators.
Not only is the location of the eyes on humans an advantage, but having two eyes instead of one, allows humans to perform many daily tasks with greater ease. This is called binocular disparity, which is the difference between the two retinal images of the same scene. Disparity is the basis for stereopsis, a vivid perception of the three-dimensional world that one cannot perceive with monocular vision. Stereopsis is the ability to use binocular disparity as a cue to depth. Depth cues are information about the third dimension (depth) of visual space, and they can be monocular or binocular. A monocular depth cue is available even when only one eye is being used to see the world. A binocular depth cue relies on information from both eyes. I enjoyed reading about this related concept because after reading so much about the anatomy and physiology of the eye this semester, I have really become interested in all the areas of how we perceive the world through vision. I now have a greater appreciation for the entire process required for me to just see the word I typed on the computer screen, and everything else around me.
I also found the concept of motion cues to be particularly interesting, especially the nonpictorial depth cue called motion parallax. A motion parallax is an important cue to depth based on head movement. The geometric information obtained from an eye in two different positions at two different times is similar to the information from two eyes in different positions in the head at the same time. The example used in the textbook to explain this concept was very helpful to me. It said to imagine yourself looking out a train window, and the scenes you see change each second as the train moves from left to right. The objects in the scene outside the train move right to left, with the closest objects appearing to move the farthest across your visual field, and the farthest objects appearing to barely move at all. Motion parallax is another cue that gives relative metrical information about how far away objects are from you. It can even provide a sense of depth in situations where other cues aren’t very effective. I thought it was interesting that motion parallax is similar to stereopsis, after understanding what each of these concepts means, it is easier for me to think about the similarities in these terms.
While finding many concepts interesting to learn about, I didn’t enjoy reading about stereoblindness. Stereoblindness is an inablility to make use of binocular disparity as a depth cue. This term is typically used to describe individuals with vision in both eyes. An individual who loses one or both eyes is not usually referred to as stereoblind. The 3-5% of the population that lack stereoscopic depth perception have stereoblindness. This condition is usually a secondary effect of childhood visual disorders, like strabismus, in which both eyes are misaligned. I think this is an important topic to learn about from the chapter, but I just did not find it as interesting as some of the other concepts.
I think understanding the concept of binocular disparity will be very useful in helping me understand sensation and perception. Disparity is the basis for a vivid perception of the three-dimensionality of the world that is not available with only monocular vision. I think being able to use stereopsis is important for safety and survival in humans; thus we should take the time to learn about how most of our eyes are allowing us to perceive the world around us. I know that I often joke about having poor depth perception, but I am thankful that I am able to perceive how far away important objects like stairs, doors, edges of cliffs, and so on, are from me. I never knew how my eyes, and then brain, were able to sense and then perceive the distance of objects around me so I didn’t run into them, or look like a fool reaching for something that was four feet away from my hands.
I would like more information about the concept of texture gradient because I thought it was interesting, and something you had discussed briefly during your “How the brain lies” presentation, but want a more detailed explanation. I think it’s interesting that this is a depth cue that is based on the geometric fact that items of the same size form smaller images when they are farther away. This allows a two-dimensional image to appear to have depth, more easily detected if the smaller images are grouped separately from the larger images.
I also would like more information about corresponding retinal points. I understand that this is a geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye, but I think I would feel more confident about the concept if I could have further explanation.
Terms: binocular summation, visual fields, binocular disparity, retinal images, stereopsis, monocular vision, depth cues, motion cues, nonpictorial depth cue, motion parallax, stereoblindness, texture gradient, depth, corresponding retinal points, retina, monocular retinal images, fovea
Wow, you learned a lot! Great! I'm excited to see what you blogged about for your specific research topic from this chapter.
As I started reading chapter six I came across an interesting statement, “We challenge you to find a situation in normal life where nothing blocks your view of anything else”. If everyone takes just a moment to really contemplate what this message is saying, we are able to understand the concept of what is known as occlusion. Occlusion is involved with depth order and objects that hinder the view from other objects. An example of occlusion may be attributed to standing across a street while looking at a house that you can clearly identify, however a tree is covering part of the house from the front lawn. Another reason I find much interest in occlusion is because similarly to the concept of edges, my previous chapter four post explained middle vision and edges, which are much related to the concepts of occlusion. Middle vision is the mediate vision level between low-level vision and high-level vision. The idea shared with occlusion is that middle vision takes a visual scene and takes it apart into groups where we can understand and recognize things as separate objects. Similarly, edges do come to a stop. This is because some sort of obstruction has occurred. The Kanizsa figure is an example of this concept. The Kanizsa figure is a common figure that also helps to describe the illusory contour. This is a perceived visual. We perceive edges from the white color because of this effect. Another related topic I found interesting that deals with monocular cues was the section on size and position cues. We consider perception on the three dimensional aspect. Similarly to how color was defined in the previous chapter about color space being on a three dimensional world, due to the three cone receptors of S-cones, M-comes, and L-cones, projective geometry helps explain how we place our three dimensional visual onto a 2 dimensional surface. In this instance parallel lines converge. It is also important to note that smaller things appear to be further away as compared to larger objects. Our depth cue is relevant to relative size. Our brain is tricking us into believing that there is some sort of difference in the depths of objects. Some objects, however, we perceive based on familiar size. Familiar size is interesting because it’s something we expect and ultimately know. We have some expectations based on previous and learned experiences. For example, the image in figure 6.11 with the woman holding her hand out. The larger hand makes us believe she is fully outstretching her arm because her hand is much larger in front of her in the picture. The other image is familiar of a bend and lowered arm because the hand is more proportional to her body size. Depth cues are fascinating because of how our mind sees everything, when the brain is lying to us about the actuality of events and images. Pictorial depth cues are another great example of this concept and something I find really interesting. Artists such as Kurt Wenner are experts at depth perception and incorporate it into artistic images. The basic idea of pictorial depth cues is for the artist to use the idea of our three dimensional world and place it onto a 2 dimensional surface that gives us the illusory image of it still being three dimensional. Similarly the term Anamorphis projection also gives a great example of how artists portray their art forms in two-dimension. With the proper angel an image, such as those done by chalk artists on streets, looks correct, when it is actually very much distorted. The least interesting bit of information was the random dot stereograms. This consists of some sort of grid or surface area with many randomly placed dots. These produce no monocular depth cues. I probably like this least of all since my whole interest is involved in monocular depth cues. There is also some confusion in this area for me trying to understand the actual idea of the picture in figure 6.2. The best thing for me to understand this chapter and how it relates to sensation and perception is the continuation of the three dimensional concept and also the depth perception cues we see in two dimension. It’s important to realize how the brain sends us messages about what we are seeing, but they may not always be correct. As humans we have a hard time understanding certain components of images on two dimensional platforms. Two terms from the chapter I would further enjoy looking into are two types of disparity, absolute and relative.
Terms: occlusion, middle vision, illusory contour, color space, projective geometry, relative size, familiar size, pictorial depth cue, anamorphic projection, RDS.
Check out some paintings by Alex Gray. Lots of depth in his art and most of it seems very centered in exploring the mind using art.
I really enjoyed the demonstration in the chapter that instructed you to hold your left hand out in front of you with your left eye closed and put your right finger in front of your eye then open your left eye. I thought it was cool that your fingers perceptually switched places. This demonstrates that perceptually we construct our world in a Non-Euclidean way. Euclidean means that the parallel lines of the world remain parallel at they are extended in space. This exercise demonstrates that our perception is actually Non-Euclidean. Humans have two eyes, and our visual system is able to reconcile the differences in perception from the two images our retinas perceive. I also didn’t know that rabbits can see a full 360 degrees compared to human’s 190 degrees. Therefore rabbits can see straight up. I thought that was interesting.
The question was raised in the book, “why did humans evolve to have two eyes” was interesting to me. This fits in the chapter because it is important to understand how our two eyes work together to form the images that we see. Our perception would be different if we only had one eye. The obvious answer to the question would be that it is in case we loose one we have a spare. This is a good point. But the demonstration in the book adds other reasons to the list. Binocular summation is an advantage that mammal’s faces and some birds have the advantage of having. This is the advantage of detecting a stimulus with two eyes instead of just one eye. The book suggested trying to put a cap on a pen with just one eye and then repeat the process with both eyes and note the differences. I found it took much more time to do it with just my one eye. The difference between two retinal images of the world is known as binocular disparity. The 3 dimensional world would not be as vivid with monocular or one eyed vision. It would also effect stereopsis or the use binocular disparity to give one depth perception.
I also liked the part of the chapter that discussed monocular cues, a depth cues that is available even when the word is viewed by one eye alone. A big part of how our brain interprets depth is through occlusion. Occlusion is a nonmetrical depth cue which basically says that when an object is overlapping with another object one appears to be closer than the other object. This however does not give one any information about the size of the object that is being overlapped. Without metrical depth cues we may perceive objects at being much closer, much farther away because we would not be able to perceive distance of objects. The depth cue of relative size helps with this. It is a comparison of size between items without knowing the absolute size of either one. Basically it is the law that things that are smaller are farther away. There were two figures in the book. One that demonstrated relative size it was a page full of pictures of pennies that were different sizes to demonstrate that the smaller ones looked more distant because they were different sizes. Another figure in the book was a picture of different sized bunnies. This time the smaller ones were congested at the top of the page and as the rows got closer to the bottom of the page the bunnies got bigger. This demonstrates texture gradient. This is a depth cue based on the geometric fact that items of the same size form smaller images when they are farther away. This means that as the bunnies change size across the image surface depth will form. I thought this whole topic of depth was really interesting because even though the page is flat we can create a depth in our perception. I just think that is cool. We also can learn about what size things should be in comparison to other items. This depth cue is called the familiar size depth cue. This explains that we know about what size a hand is, and based on how big it is in comparison to other items in our view we can determine how far it is away from us.
One thing I didn’t enjoy as much in the chapter was the part about random dot stereograms. I didn’t understand the figure in the book with the squares. Random dot stereograms are pictures made out of a large number of randomly placed dots. One then makes inferences about depth in the picture to make sense of the image. The book says that you can not see the images presented in the squares with monocular vision alone (one eye closed). You can only interpret them that way using binocular disparity. I don’t really understand what they are trying to say in this part of the chapter because I cannot get an image using both of my eyes. Bela Jelesz a Hungarian radar engineer referred to the stimuli that is defined by binocular disparity alone as cyclopean.
I think the most useful thing in this chapter when attempting to understand sensation and perception is understanding depth perception and all the different little things about it that make us see what we see using the two eyes that we have.
Some things that I would like to learn more about in class would be illusions and the construction space, and the physiological basis of stereopsis.
Terms- Non Euclidean, binocular summation, binocular disparity, monocular, stereopsis, monocular cues, nonmetrical depth cue, occlusion, metrical depth cues, relative size, texture gradient, familiar size, random dot stereograms, cyclopean, Bela Jelesz
Pretty interesting stuff that again lets us know that we don't really experience the world as it actually is, but rather, based on the expectations and probabilities that the brain computes. The linear perspective is pretty interesting and as unsafe as it is, I always like to stare down the line of train tracks off into the distance to remind myself of how my brain lies to me about what is ahead.
In this chapter I read a lot about perception in different ways. Once more I was interested in how my artistic background is being brought into the topic of this class. Perception and what the eyes do while perceiving can be rather interesting. I found binocular summation, the combination of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone. It puts to mind how much we take for granted with even with both eyes, when there are people who are monocular, being with one eye, or blind and have neither. How our vision allows us as superior predators to seek out the smaller things, while rabbits have a wider range of vision so to detect those predators. Texture gradient was another topic I found interesting in this chapter. Being it was mentioned earlier in the class with the example with a woman in a chair, that same woman in the same chair down the hall. When the fair back woman is brought forward, our perception is distorted and we see that the far back woman is far smaller than the one in the foreground. Amazing what our eyes can interpret and once taken out of that state, how confusing it can be. This is best expressed with anamorphic projecting. The use of rules of linear perspective to create a two-dimensional image so distorted that it looks correct only when viewed from a special angle or with a mirror that counters the distortion. The street artist whose work was put into the book caught my attention due to the fact that I’ve recently seen works of similar nature. Rather they were painted onto a sheet of cloth/canvas o spread across the floor to give the impression of a crocodile invested waters in the middle of living room. Which much to my frustration I cannot find in order to show.
Perhaps my least interesting thing in this chapter is occlusion. Occlusion being the cue to relative depth order in which, for example, one object, obstructs the view of a part of another object. This is once more a relation to art, and I’ve known for a while about this particular thing, just never had a name for it; now I do. Though it was interesting, it was probably the least interesting. What’s most interesting to me is just how much of my background in art begins to come out of the woodwork as the class goes on, yet it isn’t exactly unsurprising when it’s dealing with perception. As the artist usually interprets what they see in the world or what they see in their mind. I think knowing some of these quirks our vision seem to have is most useful in not only know what causes it or having that knowledge. Gives us more to learn and realize just how much our vision continues to fool us.
Topics to talk about in class; aerial perspective, stereoscopes and stereograms
Terms: monocular, texture gradient, occlusion, anamorphic projecting, binocular summation, linear perspective
I think occlusion seems less interesting because it seems so obvious to us and is more intuitive. It's like, yeah if something is behind something else, it is further away. I'd love to see the crocs in the living room paiting if you find it. Sounds very unique and different from what occurs in our natural world.
I found the evolution of our visual field and eye placement to be extremely interesting. I was not aware of how and why different species of life had different visual fields for very specific reasons. Different binocular visual fields give all sorts of life different cues to stay alive. The book used the rabbit as an example. Rabbits can see a full 360 degrees around their heads, while humans can only see about 190. Binocular summation, according to the book may have also partaken in the evolution of visual perception for birds and mammals.
I also found haze or aerial perspective really interesting because, well I'm not sure if i really understand why, but it explains why the sky is blue!! The understanding that light is scattered by the atmosphere, and that short wavelengths (blue) are scattered, thus being the sky. You can't pass by this while reading it and not think it is interesting. I mean, how many times does someone ask you, "why is the sky blue". Now I know the answer! Haha.
The third thing I found most interesting about this chapter is the technique they call anamorphasis or anamorphic projection. I have seen so many different pictures on the internet of paintings people have drawn on streets and buildings and other odd places that in on way looked like a drawn or painted on picture. It looked like you could hop right into it! What it does is pushes our three dimension world into a two dimension and it just blows our mind. There are some good examples in the book. It all seems to matter on how you look at the picture. When you look at the same image at a different angle, the picture will seem extra stretched out, or condensed in. Trippy!
One part I did not find interesting was the last part on abnormal visual experiences. This is different for me because I often have found the abnormalities of these chapters to be the most interesting. I am not sure if it was because this chapter was so long, or if I really enjoyed the rest of the chapter besides this. Either reason can be correct. I really enjoyed reading about everything else in this chapter, so reading about the abnormalities seemed less appealing to me this time around.
I think a lot of this stuff will be extremely helpful in understanding sensation and perception. Everything on depth will be very helpful because, we now have a better understanding of how and why we see this way. Oh, and I can explain why the sky is blue!!!
One thing I would like to learn more about is the philosophical topics at the very beginning of the chapter. Another would be the horopter area and Panum's fusional area. This seems really interesting to me and I would love to research it more!
Terms: binocular, binocular summation, haze, aerial perspective, anamorphosis, anamorphic project, horopter, panum's fusional area
Hopefully you did research those things more in your next post! The blue sky is always interesting to learn about. I think the paintings on buildings and random objects present in cities and towns are some of the most interesting perceptual experiences. If you ever get a chance to go to San Francisco, CA, you'll see a lot of these paintings in the most random places, but it all adds to the unique memorable perceptual experience.
While I was reading chapter six I found most of the information to be interesting. This chapter had a lot of information to take it. I also enjoyed this chapter because for the most part it was very easy to understand and I could relate it to real life examples
from the examples that were given in the book.
One of the topics I found to be most interesting was the information on the stereoscopes and stereograms. This was a section that caught my attention because I found the stereoscope to be very technological for its time. The stereoscope also helps to demonstrate and illustrate how our binocular vision works. They make it clear that there are depth cues. The stereoscopes really helped the understanding that our left and right retinas see images and objects differently. I also found it interesting that the stereoscopes were in a way like today’s three-dimensional glasses, and they helped people see photos in three dimensions.
Free fusion was also discussed in the section about stereographs because it is another way someone can accomplish seeing what is seen with a stereoscope without using one. This topic was interesting to me because in free fusion you can see the depth cues by crossing or converging your eyes while looking at two different images that are similar. Free fusion can be a difficult task to accomplish, but it can be done. When free fusion is accomplished you can focus on the middle vision and see the depth of objects. Also the images that were in the left and right retinas will switch and you will see the opposite in each retina. Free fusion can be difficult for some people to perceive but that does not mean the person is stereoblind (where they lack stereoscopic depth perception) it just means they may have to keep trying. Although some of the information about free fusion was difficult to understand I found the topic to be interesting and I found myself always going back to the example to see if I could accomplish it.
Another section I found to be interesting was the section of the development of binocular vision and stereopsis in infants. This section was fascinating to me because I have always thought this took a lot of time to develop and vision was never fully developed until later on in life, but in recent years that has been proven wrong. After I read the chapter I found that binocular vision and stereopsis is developed very quickly in infants, and they also do not need much time for them to develop to adult levels. It has pretty much been proven wrong that stereopsis gets better as the child get older. Infants usually develop stereopsis around the age of four months and it reaches an adult level by the age of six months, this has been measured by stereoacuity (measures the smallest binocular disparity that can generate depth sensation).
The most uninteresting topic to me in the chapter was the information about the psychological basis of stereopsis. The main reason I found this topic to be uninteresting is because it was really the only section in the chapter that I found to be boring and dry. It was hard for me to focus during this section and I found myself having to go back and re read. The binocular neuron was hard for me to understand and I didn’t really understand how the binocular neurons relate to the retinal images from our left and right eye. I would like to better understand how the neurons are triggered and what stimulus is required. Although this section was a bit hard for me to understand I did grasp the information about absolute disparity (rotating your eyes to fixate on one image) and relative disparity (perceiving the depth between two objects).
I believe the most important idea in the chapter that is essential in understanding sensation and perception would be all of the information about the cues. I believe the cues are most important because they are a main source on how we visually perceive images and objects. I also believe the cues are important because they help us perceive the real world.
I would like to know more about the development of binocular vision and stereopsis in infants. This topic fascinates me because it develops so quickly. I would also like to know more information about how stereoacuity is measured. Along with wanting to know more about the development of binocular vision and stereopsis in infants. I would like to know more about the stereoscope. I would like to see more of the images that have been taken on the device, and I also think it is a very sophisticated device for its time.
Terms: stereoscopes, binocular vision, depth cues, retinas, free fusion, stereoblind, stereopsis, stereoacuity, binocular neuron, absolute disparity, relative disparity
There are a lot of different types of stereoscopes. You can build one with some mirrors and a few enclosures that are at the perfect angle relative to the position of the mirrors. The cool thing I find about this stuff is the fact that we have binocular rivalry and you get suppression of one image and dominance of the other image when you have this fusion going on.
As usual, I was most interested in the physiological basis of stereopsis. As discovered earlier, two neurons from the two retinas converge at the visual cortex. So, although the retinas and the lateral geniculate nuclei have the information, it is at the primary visual cortex where binocular vision first becomes sensed. In the previous chapters, it may have seem redundant to have two separate neurons converging at the same place, but it is only until this chapter that we have found the use for this anatomy. By having separate neurons a respective places in the retina, you are able to get a grasp of the difference between the eyes in the scene. These differences are the building blocks of binocular depth.
It is also interesting to note that more than half of the neurons in the posterior area of the visual cortex are tuned for differences between the two eyes. This just shows that sheer amount of effect that binocular vision has had on evolution, and has on current perception.
Another area I was interested in was the Bayesian Approach. I wasn't particularly interested in the math behind the idea, but the idea itself. This idea is based upon the fact that visual sensation is frequently tuned and re-tuned by current experiences. Most tuning probably takes place in early development; however, it is interesting to note that our sensory system is provided the materials and no instructions at birth, and the instructions are written, erased, and rewritten throughout early life. Now, perceptual objects, such as the pennies example give in the book, are quickly analyzed and perceived to be congruent with most experiences with that object. Some interesting sensory development research could be done with this phenomenon.
The topic that I wasn't particularly interested in this chapter was the abnormal experiences and how the disrupt binocular vision section. This opinion is solely based upon my bias of not liking abnormal cases, and it does provide an insight to the binocular visual system; however, this wasn't as interesting to me as learning about the concept of the binocular visual system.
I would be interested in learning more on the physiological basis of stereopsis and the Bayesian Approach.
Terms: stereopsis, PVC, LGN, Bayesian approach, development of the sensory system
I rarely hear of people who like the Bayesian approach. Usually the math turns people off, but I'm glad you could see through to the bigger picture which allows the brain to make inferences based on the probability of things happening in the world based on what has happened before. Hopefully you guys discussed in more detail.
One topic I found interesting about Chapter 6 was the idea as to why we had two eyes. The book explains that it is the same concept as to why we have two lungs, two kidneys, and two brain hemispheres. By having two eyes, we can see the world around us much better than if we only had one eye. If we were to lose one eye than we could still be able to see with the other eye that was not lost. What I also found interesting was that a rabbit has 360 degrees of a visual field whereas humans only have around 190 degrees. By having the limited visual field of 190 degrees, it gives us the distinct opportunity to be able to see fast, small moving objects in front of them. This degree of visual perceptiveness is called binocular summation. This is the combination of having two eyes, which makes tasks much easier than if you only had one eye. Although we have two eyes, the issue of binocular disparity occurs often. This is the small visual differences between both retinal images of the same visual scene.
Occlusion was something that was mentioned in Chapter 4, but was brought up in Chapter 6 as well, as it is having to do with depth perception in a three-dimensional world. As a depth cue, occlusion gives us information about the relative position of objects in a visual space. Occlusion is visible in almost every scene we encounter in life and is the most reliable of all the depth cues. Occlusion can only be debunked if you were to look at three shapes (a triangle, square and circle are shown as an example in the book) and the frontal most object is fully shown where the second most frontal object is somewhat covered, as well as the thirdly most frontal object is covered by the second object. Occlusion can only be debunked if the second and third objects were just oddly shaped like puzzle pieces. Occlusion is actually considered to be a nonmetrical depth cue, this means that it only provides information about the depth order and not the depth magnitude. A metrical depth cue is one that provides information about distance in a three dimensional situation.
Pictorial depth cues are those that distance or depth are used by artists to create a three-dimensional picture on a two-dimensional surface which can be viewed by multiple angles. To correctly interpret a three-demensional image on a two demensioanl surface, the viewer or artist has to take into account the idea that the picture itself is flat and that the three-demensinal image that is displayed is not actually real. Our visual perception compensates for perceptual distortions in pictures. Sometimes artists or photographers use a technique called anamorphic projection. This is when they use the rules of linear perspective to create a two dimensional image so distorted that it only looks correct when it is viewed from a special angle.
The thing I found least interesting was the Vieth-Muller circle. I didn’t really find this interesting because it was just confusing. This is a graph that shows the visual disparity of objects and where they lie on corresponding points. This circle also brings into account the Panum’s fusional area. This is the region of space in front of and behind the horopter, within which binocular vision is possible. I think that the section about all the pictoral depth cues is the thing that I most enjoyed aobut the chapter and would get the most from. This will help us understand sensation and perception because it helps us understand how we are able to see and tell the difference between visual disparities and visual stimuluses in two/three demensional scenes.
TERMS: binocular summation, binocular disparity, occlusion, depth cue, nonmetrical depth cue, metrical depth cue, pictorial depth cues , anamorphic projection, Vieth-Muller circle, Panum’s fusional area, horopter
Yeah I'm with you on the horopter. Really heavy optics and physics stuff going on with that. I get the point, but totally lose interest pretty quick. Glad the other stuff made sense and was interesting to you.
I was interested in reading about how the retina goes about interpreting depth perception. Typically, humans use two eyes to perceive their visual field, this is called binocular vision. This being said, humans can use this form of vision to see up to 190 degrees of their visual field, the placement and direction of the eyes on the head determine how much space can be viewed at once. Binocular summation is the overlapping of visual fields, or when the visual perception from each eye combines with one another, forming a unique image. There are parts of the visual field that do overlap and there are parts that do not. When the images do not overlap then there is a binocular disparity. Binocular disparities are images that are unique to one specific visual field, or they are the differences in what each eye sees. Binocular disparity is what gives a vivid perception of three dimensional images. Vivid is the keyword in this sentence because it is still possible to experience visual depth without binocular vision.
Stereopsis is defined as the perception of visual depth using binocular cues, but this is not the only way to perceive depth. Monocular vision is when only one eye is used to interpret the visual space. Those who depend on monocular vision learn to perceive depth; it just takes time to adjust. Though the depth perception may not be as vivid as binocular vision, it is still possible. Both monocular and binocular visual systems use a set of depth cues to determine visual depth. These cues combine to help explain the images that are interpreted.
I was particularly interested in monocular cues and how one could still sense depth with only one eye. Occlusion is one monocular cue that helps tell the difference between the positions of objects by defining the lines and edges of these objects in view. Occlusion allows us to recognize the edge of table and know not to walk into it. Without this, our visual system would not be able to tell the difference between objects. Size and position cues are also very important for monocular vision. Relative size is when the retina judges the size of an object by comparing it to the objects around it. The book gave a clear example of when the retina encounters a small object, it is assumed to be far away, this is because of the comparison to the other objects in the frame. Texture gradient is a depth cue that is comparable to relative size because it compares item size to the distance. More specifically, texture gradient explains that if the same object is multiplied into several different sizes, then the objects that are smaller will appear farther away. Another important depth cue is relative height. The distance of an object is determined by where on the retina the object is viewed. If the object is high on the visual plane, then it would be determined as farther away. Monocular views become three dimensional when relative size and relative height combine on the visual field.
I found the Vieth-Müller circle to be very confusing and after trying to read and re-read, I still do not understand this concept. The way I understand it is that there are points on the retina that have zero binocular disparity, meaning no overlap between visual cues of each eye. This spot can be determined by calculating the angle and plotting it onto a circle. The area of zero binocular disparity is called the horopter. I also understand that the Vieth-Müller circle and the horopter are not the same thing, but this does not make this concept clear.
A good topic for class would be the vanishing point, because I feel like I could use more information about this topic. I would also like more in depth information about monocular cues and how they differ from binocular cues.
Terms: depth perception, visual field, binocular vision, binocular summation, visual perception, binocular disparity, stereopsis, monocular vision, depth cues, occlusion, relative size, retina, texture gradient, relative height, horopter, Vieth-Müller circle.
Yeah, the horopter stuff is pretty tough. I think it is giving you an idea about how complex the physics and optics of the eyes and the visual system really is. Hopefully you guys will discuss the vanishing point more in class.
Chapter 6 was a pretty fun chapter to read. I liked the fact that it focused more on what we are seeing with our eyes rather than the biology of our eyes. The first interesting thing I read about was Occlusion. Occlusion is when our eyes infer relative depth perception. The book had a good example of a circle in front of a square in front of a triangle. We are able to tell what order each shape is in because each shape obstructs the view of the shape behind it. Occlusion can only provide a non-metrical depth cue which means we can only see the depth order and not the depth magnitude of each shape. A metrical depth cue shows us the order of the shapes and provides information about the distance in the third dimension. Occlusion, I thought, was a good example of stereopsis. We use the cues from our binocular vision of objects to form binocular disparity which is the basis of stereopsis. What I’m basically saying is when we see objects in our field of vision; we estimate how far one another are from us by comparing the depth of each object to each other. I thought it was very informing to me to find out that’s how we judge depth.
Another topic I found interesting was texture gradient. Texture gradient’s definition from the book is a depth cue based on the geometric fact that items of the same size form smaller images when they are farther away. An array of items that change in size across the image will appear to form a surface depth. The book had a good example of this with a picture a bunch of rabbits. The rabbits in the front of the picture look like they are much bigger but if you take the rabbits from the back row and scale them up; you’ll see that they are the same size. We measure the size of the rabbits by how close we stand to them. If we view two rabbits in a picture and we think just because the rabbit in the front is the same size as the rabbit in the back that the rabbit in the front must be smaller. That isn’t the case according to relative height. Relative height tells us that when we stand, objects that are further away will be higher up. So the rabbit we see in the back when we are standing in front of them will look bigger than the rabbit in the front but really they are the same size. I found this to be interesting because it went a long with your presentation you gave a couple of weeks ago, so it was easy to try that in with the book.
One final thing I found interesting was anamorphosis. Anamorphosis when an artist uses the rules of linear perspective to create a two-dimensional image so distorted that it looks correct only when viewed from a special angle or with a mirror that counters the distortion. What that definition is basically saying is that we are taking a 3-dimensional image into a 2-dimensional image. Linear perspective is a depth cue based on the fact that lines that are parallel in the three-dimensional world will appear to converge in a two-dimensional image. That’s how we get a lot of vanishing points in anamorphosis images, which is the point at which parallel lines receding in depth converge.
Incorporating pictorial depth cues which are cues used to show depth in a 2-dimensinal are also another way we can make a 2-d picture look 3-d. I just really found the images in the book really fascinating. It was crazy see the image from one angle and not being able to figure out what it is but then seeing it from the correct view point and seeing a whole new picture develop.
I liked reading about horopter and diplopia but I really didn’t understand what was meant about the surface of zero disparity and what the convergence of our eyes has to do with that. From what I read that things outside the horopter seem to have more of a double vision look, where both eyes see a different image but I really didn’t understand entire concept.
If there’s one thing I took away from this chapter that’s relevant to the class is stereopsis and binocular disparity. I found it very interesting that we use the cues of objects we see and compare them to other objects to figure out distance.
Two topics I would like to learn more about would be the horopter, diplopia, and the Bayesian approach.
Terms: binocular disparity, stereopsis, occlusion, nonmetrical depth cue, metrical depth cue, texture gradient, relative height, linear perspective, vanishing point, pictorial depth cue, anamorphosis, horopter, diplopia, Bayesian Approach.
Pretty neat how artists can take advantage of what they know of the visual system and turn something we usually experience 3D into a 2D that still looks 3D in some respects. This is interesting indeed.
The first thing that I found interesting was the pictorial depth cue. It’s a relatively easy concept when you put it into practice. I remember learning it in art class. The picture of the two story house I drew as a freshman might still be in my parent’s basement somewhere. You start with a straight line down the middle of your paper (it should be really faint) this will serve as the point closest to the observer. It can really be anywhere on the paper, in class we used it as the side of the house that was closest to us. Then you put two parallel dots at either side of the paper, typically they tend to be in the middle of the length of paper. Then all the lines from the center line go to the dotes on either side of the paper. The dots will act as a vanishing point. Then, everything just gets smaller from the center line making it look farther away because it is proportionally smaller in size compared to things close to the center line. Anamorphosis or anamorphic projection was always fun to play with. I used to get one or two in the puzzle books that my grandparents would get me. Honestly I didn’t even know it had an actual name, but I found it interesting. The final thing I found interesting was the motion parallax. Even though the book says that you don’t need to be on a train to experience it, I find that train and car are the best way to experience it. I remember being on a train from Mount Pleasant to Chicago and the motion parallax was really confusing at first. We traveled though a lot of farm land so the farm houses that were probably over a mile away seemed to be moving at their regular speed. I had travelled a lot with my family before but it was mostly by car. It wasn’t until I looked at the ground closest to the car or train that I noticed the difference in speed. In a car you can still pick out a flower from 5-10 feet away, but it a train everything was going by so fast that it had to about 25 feet way to make anything out.
It wasn’t terrible but all of the terms for the little things that the eye does based on the image it was looking at did get a little boring.
How in general the brain will fill in what they eye is taking in. Like how the brain uses it’s pre-exsisting knowledge of relative size to make a judgment of distance when comparing two objects. Like cars that are far away from each other in an almost empty parking lot. Or how it compares objects using occlusion when it sees one object is covering up a part of another object. Like how cars will block the view of other cars when they are all lined up in a row.
Corresponding retinal points and stereoblindness. I just want some better examples of corresponding retinal points because I had a little trouble putting it into prospective when just reading it in the book (pictures didn’t help much either). And like with other conditions in earlier chapters, I would just like to know more in general about stereoblindness. For example; how many people are diagnosed with stereoblindness? Is there a way to correct it? How do people who have stereoblindness adapt (if possible)?
Terms: pictorial depth cue, vanishing point, anamorphosis or anamorphic projection, motion parallax, relative size, occlusion, corresponding retinal points, and stereoblindness.
You could do some research for your next blog post to answer these questions you posed. I think that would be cool to learn more about. Interesting that you took your own perceptual experience with motion paralax and applied it the the formal definitions you learned here.
After reading chapter 6 I was surprised at how much I truly didn’t know about space perception and binocular vision. The first thing I really enjoyed learning about was the difficulty of matching an image element in one eye with the correct element in the other eye. This is known as the correspondence problem. Another fact that I thought was interesting was that all of the various monocular and binocular depth cues are combined (unconsciously) according to what prior knowledge tells us about the probability of the current event. Illusions are caused by making the wrong guess. I also found the subject stereopsis very interesting. Stereopsis emerges at around 4 months in humans which can be considered a critical period for development; it can be disrupted through abnormal visual expression early in life. The third thing I found to be very interesting in chapter 6, was why exactly humans have 2 eyes and why they are so important to us. Having two eyes is an advantage for a large amount of reasons. Some of the advantages are that having two eyes expands the visual field, providing redundancy is one eye is damaged and also permitting binocular summation.
The binocular rivalry was something I could incorporate into my current knowledge. The binocular rivalry is the competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes. Another item I read about that caught my attention due to the fact of how thankful I don’t have it is strabismus. A strabismus is a misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye on a nonfoveal area of the other eye. Something that I didn’t really enjoy when reading this chapter was Bayesian approach. The bayesia approach is a statistical based on Reverend Thomas Bayes’ insight that prior knowledge could influence our estimates of the probability of a current event. I believe understanding suppression and binocular rivarly will help us better understand sensation and perception. Two items I would like a better understanding about is space perception and binocular vision is illusions and the construction of space; also combining depth cues in general.
Term: Correspondence problem, monocular, binocular, depth cues, illusions, stereopsis, binocular summation, Bayesian approach, binocular rivalry, strabismus, fovea, critical period.
Glad you got some insight into the functions of these two things you use all the time!
I was immediately interested in the fact statements about the advantages of having two eyes. The advantages of having two eyes hinge on the fact that having to eyes makes life easier. The book talks about evolutionary pressures, and how being able to see more makes survival more attainable. It also discusses binocular disparity. This is how the world is viewed in all three dimensions. When the world is viewed in a monocular way depth is not perceived. I had never put much thought to what two eyes did that one eye could not, but the more I read the more essential have two eyes appeared to be to me.
I was intrigued by the discussion of binocular rivalry and suppression. This topic was something I have thought about for a long time. How do our eyes decide what it is that we will see? The answer is that the focus will be on the more interesting, or more active thing. That makes sense to me because I think about the conversation we had in class about why we are not always aware of our nose. We tend to discount things that are constant or boring so with that being said it only makes sense why we see what we see. I also liked this section because the experimental activity was easy to do.
Anamorphisis was another cool concept in the chapter. I liked it because you are eyes are really tricked into seeing things in a different way than what they really are. Anamorphism is done based on the rules of linear perspective. Linear perspective is the fact that lines that are parallel in three dimensions converge in two dimensions. Just looking at the way the artist could trick the eyes in the examples were amazing.
The section of this chapter that was the least interesting to me was the section that discussed disparity. I understood that it was talking about what an individual focused on and how that would appear to them. it would appear differently in uncrossed disparity as opposed to crossed disparity. Uncrossed disparity means that the images of objects located behind the horopter are to the right in the right eye and the left in the left eye. In crossed disparity it would be opposite. Horopter is the location of object whose images lie on corresponding points. It is the surface of zero disparity. What made this section uninteresting to me was that the more stuff they placed in the visual field the more confusing things appear to show up so that was hard for me to comprehend.
The most important thing to take from this chapter is that Binocular vision makes everyday things so much easier. The most important concept from the entire chapter to me is Binocular summation. Binocular summation means that the signals from each eye combine to makes performing task easier than they would be otherwise. When I think about the importance of binocular summation and also the fact that two eyes give you a wider field of vision I think of survival. The book talked about how it makes it how it would improve looking for dinner. I think more about how binocular vision could also help you steer clear from danger in many different ways. Also if the two eyes were unable to combine what they were seeing then we would have binocular rivalry that was won by one of the eyes.
All in all I would say that there were not any concept that I felt the book short changed me on. If I had to choose something to learn more about I would like to learn more about the motion parallax and also corresponding retinal points.
Key terms: binocular rivalry, binocular suppression, crossed disparity, uncrossed disparity, horopter, monocular, anamorphisis, linear perspective
I think you'd like the binocular vision chapter from Mark Changizi's "The Vision Revolution" book. It's kind of a theoretical cognitive science evolutionary perspective book, but it has a different account of why have binocular vision. You might check it out if interested.
One of the first topics in the chapter that really tripped my trigger was the section pertaining to motion parallax. Once again, this is a depth cue to which we have grown so accustomed that we take for granted its simple complexity. This concept functions much like that of binocular vision, except that each “eye” in this analogy is actually the same scene from two different perspectives. In other words, motion serves to provide information about the relative distance of objects in much the same way that depth information is gleaned from stereoptic cues. As our viewing perspective changes, so too does the angle from which our eyes are viewing a scene. The fascinating part of this effect is that objects nearer to your eyes change position much more rapidly than those that are further away. This phenomenon is simple and seems rather intuitive, but when you really start to think about it these sorts of depth cues can be somewhat mind-boggling.
Another fun segment was the portion about stereoscopic correspondence. We also take for granted the fact that our eyes are consistently able to reconcile what is really two separate visual inputs into one cohesive visual field. Because most peoples eyes convergence and diverge at corresponding angles, this dilemma is much more easily solved. Anyone who has dealt with a lazy eye sometime in their past can probably relate to what it would be like NOT to consistently solve the correspondence problem. One way in which this problem is solved is by working inward from low-spatial-frequency characteristics to finer high-frequency details. Two additional heuristics outlined in the textbook are the uniqueness constraint and the continuity constraint. The former states that each feature or object in a scene is represented just once per retinal image. The fact that we are looking at the same objects from angles that are just a few centimeters definitely helps cut down on the number of potentially confusing dopplegangers within a field also. The continuity constraint, on the other hand, states that all neighboring points within scene should be the same relative distance from the viewer’s eyes, except at edges.
And finally, another section that I unexpectedly enjoyed was the portion about the Bayesian approach. At first glance, this portion of the chapter might seem dry because it has a bit of algebra. However, I thought the Reverend Bayes had a very clever way of approaching visual inputs. He stated that the probability of a scene is proportional to the product of its overall probability and its specific probability given its existence as a specific scene. Because so much of our perceptual system occurs below or prior to consciousness, it is difficult to rule out such a theory. Making it even more difficult is the fact that so much of our prior experiences cannot be quantified or even separately recalled. However, this quandary can be resolved somewhat by attempting to analyze a scene from the perspective of a hypothetical ideal observer. In this way, the quality of information can be employed to determine the best possible performance of someone using said information. I think the most important knowledge to be gained from this chapter is all of the subtle ways in which our brains glean visual cues from an environment in order to navigate more effectively. I would like to learn more about stereoscopes and stereograms and the physiological basis of stereopsis.
Terms: motion parallax, depth cue, stereopsis, stereoscopic correspondence, correspondence problem, uniqueness constraint, continuity constraint, Bayesian approach, ideal observer
A nice way to describe motion paralax. This does seem like a pretty advanced thing that we take for granted all the time. Interesting that you picked up on the ideal observer stuff given that most computational modelling work that uses Baysian inference is based on an ideal observer and various amounts of prior experience used to estimate probability of things occuring in the external world.
I really enjoyed this chapter because it points out a lot of little tricks that help us see 3-D figures in 2-D pictures. A lot of these things I had never thought about, but make a lot of sense. Some are cues that help us see 3-D, when it might not really be there. One such thing is occlusion. This is when a figure covers another figure in a picture, it makes it seem closer than it really is. This is a depth cue. However, this is just a heuristic that our eyes use to make us see depth. Another one is relative size. Relative size lets makes us think that smaller objects are farther away than bigger ones. All though this maybe true, an object may just be smaller. Another thing I found interesting was anamorphosis. This is purposefully distorting an image so that it is only clear what it is when viewed from a particular angle. I think this is a very interesting form of art because it literally gets you to look at it from a different view point. The third thing I found interesting was the random dot stereogram. This is a picture of thousands of small dots that without the use of both eyes we see just dots, but with both eyes, we can see shapes. We are only able to see them with the use of binocular vision and we are not able to see them with just one eye. These things were interesting to me because the book gave good examples of the ideas they were expressing. I would like more examples of these presented in class because they help me remember the concepts when I can actually see how they work. What I wonder is how long ago were we able to have the visual capabilities that we have today. I wonder if our eyesight was much better when we were hunters because that was more vital to our survival than it is today. One thing that I do not like about reading these chapters is that it makes me think about it in my everyday life. After reading the chapter, I start to notice these ideas happening in my day to day activities.
Terms: Occlusion, Depth Cue, Relative Size, random dot stereogram, random dot stereograms, binocular vision
I think the relevance to our everyday world is astounding, yet it can get a little overwhelming describing the intricacies underlying it all.
The example that Otto gave in his lecture two weeks ago about the two ladies who were sitting in the same chair, but one was farther back than the other. We all assumed that the one farther back was the same size as the one that was closest to us. However when the farther back one was placed next to the closest one, we saw how tiny the farther back one actually was. This concept is known as texture gradient. The reason that our eyes deceive us like this is because we know the size the of an actual object and automatically assume that it is correct. This concept is familiar size. Another concept about our eyes is that when we see a figure that is bigger, and a figure that is smaller, we automatically use relative metrical depth cue, which means that we know that the smaller one is farther away from us than the bigger one.
In art class, they taught us that when we are drawing in three dimensional, we need to use linear perspective where the lines come together in the back middle as an vanishing point. That way, the picture looks as though it is fading in the background, but it is still continuing. Motion parallax also happens when both of our eyes are in two different positions but trying to look at an object together. A good example of this is the street artist who draws with chalk on the ground and actually makes the drawings look like they are there, when they are really stretched apart. (You can google chalk artist images and see some examples of what I am talking about. The link was too long to add in this blog!) Stereoscopes is the act of sending one image to one eye and a different image to the other eye, which then our brain converts the two images into one image. When we look at an image and see it as one whole thing, we don't think about how our eyes are interpreting two different things and combining them, at least I don't. So it's interesting to learn about how this happens and think about how our vision would be like if we saw two different objects at the same time out of both eyes. Trippy!
Esotropia is when one of our eyes deviates inward and exotropia is when one deviates outwards. This made me think really hard for a good ten minutes about how this would differ for people who have a lazy eye that is always looking inward/outward. When our two eyes see images that confuse our brain, it's known as strabismus and to eliminate one of the images, our brain suppresses one of the images so that we only see one.
I found this whole chapter to be interesting and nothing was boring to me. Everything seemed to tickle my fancy and it all applies to sensation and perception, particularly perception, by describing how our vision system works and how we interpret images. It also discusses how our brain can play tricks on us and how it can also help us so that we aren't seeing crazy images at the same times.
I think it's interesting how scientists are able to find this information out based on their studies and how big our sensations are in playing a role in our lifes. It's amazing to think of how many people take for granted that they can see or talk or hear, but don't even realize that they are grateful for it. I don't care what we learn about next. This stuff is interesting and not boring :)
Terms: texture gradient, familiar size, relative metrical depth cue, linear perspective, vanishing point, motion parallax, stereoscopes, esotropia, exotropia, strabismus, suppresses
Wow, I had never seen the chalk artist guy before. Really grateful for you sharing that. I like the one where the guy is walking and walks around the chalk art that looks like a block of cement has been extracted from the sidewalk. Hahaha, he just looks as if he's avoiding it altogether. Very cool stuff.
I am going to begin with the part of this week’s reading that I disliked the most. What I did not like was the picture on the very first page of this chapter. My brain and my eyes when working together found this picture to be quite difficult to look at and I was only able to look at it by focusing on a single section, I was not able to assess the picture as a whole. After reading the chapter, I now have a better understand as to why I reacted in the way that I did to Escher’s work of art known as Relativity. I only began to comprehend the photo after understanding of concepts of non-Euclidean and Euclidean space. Euclidean space is a term named after Euclid an ancient geometer. The term itself is used when describing how we perceive the world around us in a realistic way. A person who identifies as a realist then would believe in Euclidean space and believe that everything we sense is real and true in the universe. In opposition to this belief would be the positivists, who would believe that the whole world could in fact be a hallucination and is made up of non-Euclidean space. Both are interesting and important concepts to look into. Since humans are such emotional creatures who perceive everything in different ways and give different meaning to what is presented in the “real world,” in my opinion both concepts are most likely working together to create the true world around us. This information was important is should prove to help in my basic understanding of sensation and perception.
I enjoyed learning about lower and higher visual fields and how this effects our perceptions of the environment. Both of these areas have to do with relative height. The lower visual field receives information from those things you see up close and are presented in our minds to be close to their actual size, whereas, items received by the higher visual field are further off in the distance. In reality when items are seen in the higher visual field, our brain distorts them and we believe that we see them as their correct size when in fact we are generally seeing a much smaller image. In my opinion, this is more evidence for the positivist ideology mentioned above.
In addition to these concepts, I also liked the example on page 140 of the women holding out her hand. This example helps us to understand how depth works. If you look at image A of the woman, our brain believes that her hand is close to your face and being held out, away from her body, because it is so large. In image B the brain thinks that she is either standing further away or that her hand is closer to her body, again because of the size presented. This is another one of those tricks that our minds play on us to help us understand the world. This concept or trick is called familiar size and as stated described helps us understand depth cues.
Another fascinating process that our brain does for us when working with depth cues is help us to understand a two-dimensional world in a three-dimensional way, such as with television or artistic works of art. This is known as pictorial depth cues. This happens on the surface of the retina and is useful for many reasons in our everyday lives. In relation to this is the vanishing point, which to me seems a little mysterious and difficult to understand but is really a common and useful piece of information that is barely noticed. This vanishing point is the point where parallel lines in a two-dimensional picture come together. In many cases, this stops the image from going on forever.
From this section is also the artistic technique known as anamorphic projection, I would be very interested in learning more about this. Anamorphic projection seems like a wacky concept as does motion cues, which I would also like to learn more about.
Terms: Escher, Relativity, non-Euclidean, Euclidean, geometer, realist, positivist, lower visual field, higher visual field, relative height, depth cues, two-dimensional, three-dimensional, pictorial depth cues, vanishing point, anamorphic projection, and motion cues.
I think most of the Escher stuff is really cool! It's definitely a bit disturbing that you can perceive something that is impossible to resolve in the external world, but that just goes to show you that our mind just lies and creates a lot of possible ways of looking at something, which are often not how the external world actually is.
In chapter 6, I found it most interesting to read about monocular depth cue and binocular depth cue and getting a unified perception of space. This was of interest to me, as my grandfather had lived the majority of his life in a monocular visional world. He was blinded in one eye at the age of fourteen and lived to the age of 77 viewing everything in his life through the remainder of his life with one eye. With the test that the text outlined for two retinal images and the differences that are displayed, with the two retinal images always differing made me wonder how he viewed things with only one eye. I am lead to assume that his total visual field was at 50% of the average human. According to the text a human visual field is more like a windshield covering a large region in front of the eyes with a 190-degree visual span, compared to a rabbit’s visual field being like a planetarium dome and a 360-degree visual span. With my grandfather’s visual impairment would be half of a windshield or approximately an 80-degree visual span, or like walking around with one eye closed at all times. His peripheral vision would be quite limited and to view the full spectrum as others, you would have to turn your head side to side to get the complete image. Obviously one would do much better at many tasks with two eyes than you would with one. Another topic that ties in to this is texture gradient. This is a depth cue that when the same items are placed farther away, they appear to form a smaller image. In my grandfather’s situation, I would assume that his visual perception was the same as those of us with a binocular depth cue, but again would have to move his head from side to side to view a full spectrum.
The topic that I found least interesting and most complex was the Vieth-Muller circle. These figures outline the location of objects as they correspond geometrically as viewed from the two retinas. If looking at one spot, it is viewed with zero disparity known as horopter. Geometry comes into play in the explanation and can be quite complex and more in depth than I find of interest.
One topic that I feel is important and most useful in understanding Sensation & Perception is size and position cues. It is important that one can view and interpret how far away an object is, or where it is positioned in comparison to other objects in order to physically make your way around in walking, driving, etc.
The two topics I would like to find more information about is anamorphic art and binocular rivalry.
TERMS: Monocular depth cue, Binocular depth cue, peripheral vision, texture gradient, Vieth-Muller circle, retina, zero disparity, horopter, and binocular rivalry.
Interesting story. I think by in large we end up being ok even with one eye. But it would be interesting to know what the differences in perception of the world would be having only one eye.
Chapter 6- Visual Attention
After reading this chapter I really enjoyed reading about how we pay attention to the one part of a scene but not another part- selective attention, learning from past experience, and inattentional blindness.
The most important topic I found during this chapter was about how people use selective attention when they are looking at the scenes around them. I can relate to this term and process because I focus my attention to what is in front of me or to things that stand out in my environment. We use selective attention because our eyes are constantly moving around and we focus on things in front of our vision or things that stand out. Our eye moments guide our eyes to focus on something. This is important to understand because paying attention contributes to many parts of life to keep you safe, or when you are at work or school.
The second topic I found interesting was learning from past experience can influence attention and what we focus on in our direct learning. If a person is driving , their focus is on the stop signs and stop lights because they know from their past learning that they need to stop or look for signs to know where to go or how fast to go. Our selective attention is used everyday, and we learn from past knowledge of particular scenes.
The third topic I found interesting was the inattentional blindness. Inattentional blindness is when a person fails to perceive something that is right in their full view. There is a perfect example of this in my life, when I am window shopping at a store. If I am at a mall and I see a cute pair of shoes in the window, I focus on the shoes, but I am inattentionally blinded by my reflection in the window. It is like when we look at the object that is desired, we ignore the reflection that is right in front of us. This particular perception happens and I never knew it had a term.
This chapter has been my favorite chapter so far because I could relate to all of the scenarios and terms. I could understand the concepts and demonstrations easier then the past chapters on neurons and the brain functions.
I found that everything I previously talked about selective attention, and experiencing is very important when we are focusing on objects around us. It is also easier to look for these unconscious habits now that I know why I am doing these things when I am perceiving something.
The two topics I would like to learn more about is attention in autistic clients and research on attention enhancing perception.
Chapter 6 in my book is titled Space Perception and Binocular Vision. I am actually very interested in reading this chapter because it is all about near and far and I am near sighted!
I enjoyed learning about retinal vision. This was amusing to me because I kept doing the little experiments that were in the book to show the difference between your right and left vision. I have always noticed and played with my eyes in a way to see things from different perspectives in different eyes, but I didn't really understand it was a scientific fact. Most things I have been learning in this book are things I have known my whole life without thinking it was important to my knowledge. Within this topic, it was also discussed why you even have two eyes at all if they each have their flaws. This is described through binocular summation in which it is discussed that two eyes are better than just one, but if you have just one, it will take over a lot of the other functionings of the missing eye.
I liked learning about depth within the size and position cues part of the chapter. It explained that when a same object is different sizes, the smaller ones look farther away even though they are just a different size. This is discussed as being relative size in which we have the tendency to compare items without knowing the actual size of either or even depth of either. I also liked the depth perception factor of texture gradient in which certain objects are lined up together that are bigger and the smaller objects are lined up on a different side giving you a sense of depth perception. This made me think back to middle school when we always had to draw depth perception and make the larger things on one end and the smaller ones on the other. We always had to have a vanishing point which was also discussed in this section. This actually makes sense to me and I would love to learn different terms that correspond with depth perception that I have always understood but didn't know it had a name.
I enjoyed learning about illusions in this chapter. The book had several examples and I was stumped by most of them. Illusions are basically where size and depth are put to the test and things that are farther away look larger or smaller even though you can't fully determine that by where the page is. I really would like to look at more illusions and see the science behind them! I will be looking this up for my topical blog this week!
I got very lost in the section about binocular vision and stereopsis. I didn't fully understand the different retinal views and their functioning. There were several different large medical words used that I couldn't figure out either. I feel this would probably be one of the more important parts of the chapter to understand, but that is how it always works, the stuff I understand is the stuff that is most important.
Retinal Vision, Binocular Summation, Relative Size, Texture Gradient, Binocular Vision, Illusions