Please
read chapter 7.
After reading chapter 7, 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 thought the part of the chapter that talks about how we perceive motion. The computation of motion in our perception was compared to a motion detector in the chapter. I thought that this made it much easier to understand. This model was developed by Werner Reichardt in the 1950s. He actually used it to explain how flies detect motion. Basically we have multiple detection cells. A fires when it detects light and then is delayed by D until it goes to X, when cell B detects light X and B fire and then it is sends it to M which signals that there is motion. This happens over and over when detecting motion. I also thought that the concept of apparent motion was interesting. This is basically when we are watching a film or television we perceive motion though the rapid firing of pictures. This is an illusory technique. They use multiple photographs or drawings and when shown at about 60 frames per second we perceive the picture changes as motion.
The are that scientists believe to be at least mostly responsible for detection of motion is the middle temporal lobe or MT. I found this part of the chapter about how they confirmed this to be interesting because it is borderline unethical in my opinion.. I don’t know.. it’s kind of extreme, but I won’t say it isn’t interesting, because it is. These researchers Newsome and Pare took a group of monkeys and trained them to be able to tell the correlation between the number of dots moving in certain directions, whether it be 100% moving a certain way, 50 percent moving a certain way, or 20% moving in a certain way. When they were done training the monkeys were so good at this they could tell when only 2-3% of the dots were moving a certain way. The researchers then made lesions in the monkey’s MT areas to see what would happen to their perception of motion. After they did that the monkeys needed about 10 times more correlated dots to be able to detect the motion of the dots. But the ability to discriminate the stationary dots was generally unimpaired. That is the really interesting part to me. That it pretty much ONLY effected their ability to detect the correlation of motion. Another thing I found really interesting about this is that in the later weeks the monkeys improved on this task and it was predicted that they were using other parts of their brains to detect motion. This is really cool to me. I wonder what would happen if they would have used a fMRI machine to look at the active parts of their brain before and after the surgery. That would have been cool. So after this experiment Newsome and his colleges took a different group of monkeys and trained them to detect the correlation of dots. Then they went in their MT areas of their brains and poked around to try to find groups of neurons that were responsible for a particular direction. They were able to isolate different sets of neurons that when stimulated would make the monkeys detect that direction of correlated dots. This is pretty cool. It “makes a strong case” that MT is the site of global motion detection neurons in the visual system.
I thought the demonstration exercise in the book with the pencil and the piece of paper was really cool and made me think a lot. Basically the book made you take a piece of paper and put a dot in the middle and only look at the dot, while moving a pencil across the paper. You perceive the dot as staying still and the pencil as moving. Then the book instructed you to only look at the eraser of the pencil while moving the pencil across the paper again. While doing this you are demonstrating what is called smooth pursuit. Smooth pursuit is type of eye movement in which the eyes move smoothly to follow a moving object. The interesting thing about this exercise is that the pencil is always the thing that appears to be moving because it is moving technically. In reality though the dot moved just as much in your visual field as the pencil did but it always appeared stationary. That is pretty cool. Can you imagine if that didn’t happen how confusing the world could be?
Something in the chapter I didn’t find as interesting was the part in the chapter about the correspondence problem. This is related to apparent motion and the motion detection theory. This is a problem faced by the motion detection system of knowing which feature in frame 2 corresponds with a particular feature in frame one. I didn’t really understand this because I wasn’t able to watch the videos as instructed in the book. I kind of got the jist of it though. The problem with the motion detection theory is that how do we know which circles correspond with each other in the two frames? It basically ends with our preceptors competing to determine what direction something is going. Something that goes hand in hand with this concept is the aperture problem. This is the concept that when something is blocking part of the visual field motion may not be able to be detected accurately.
I think the thing that is most useful in the chapter when understanding sensation and perception is the part about how our receptors work to understand and interpret motion.
Two things that I would like to learn more about in the chapter would be the physiology and types of eye movements, akinetopsia.
Terms: perception, Werner Reichardt, detection cells A, B, D, X, M, Apparent motion, middle temporal lobe, Newsome and Pare, global detection neurons, smooth pursuit, correspondence problem, Aperture, aperture problem, akinetopsia
Please make sure you edit and re-read the content of your post before you post (e.g., read your first sentence). I think the correspondence problem is important because it can be difficult for us to tie an object to a location as it moves and as there are more distractors.
This chapter proved to be quite interesting. Apparent motion seemed to be an important topic, especially since it relates to everyday life, at least for most people, as it is a major component of television. What if our brain did not perceive apparent motion, would TV not exist? How many more books could I have read up to this point in my life if apparent motion did not exist? These were a few questions that came to mind. The idea of apparent motion was identified by Sigmund Exner when doing and experiment in the lab in which he showed participants sparks of light. The sparks were coming from two different sources but the people inferred that one spark had moved to the other, really this does not even make logical sense so the spark must have been pretty amazing illusion. Sparks do not just jump voluntarily from one spot to the next. This concept of apparent motion that we see every day is an illusion that our brain uses to help us understand the world in a more orderly way will be my concept that is most important from this chapter to my understanding of sensation and perception.
When it comes to grasping the chapter another concept that intrigued me was the middle temporal lobe or MT. The understanding of the MT is essential because it was mentioned throughout the chapter. The part of the brain helps us perceive motion. The neurons in this part of the brain are none the less trained to sense motion; although they cannot do it all on their own because they do not have the color sensitive function. As a person who looks out at the world it is easy to understand why this color sensitive function is necessary as well as the ability to hear movement. I also was wondering what it might be like not to perceive motion, obviously crossing the street would be quite difficult. So I was excited when I came across Akinetopsia which is a neuropsychological disorder that effects the MT region. The people who are affected by this see snap shots of the world, sometimes they are fuzzy. I can image that a person would get used to this condition but I think it would be difficult and annoying. When the T.V. freezes on an image I always get a little frustrated wondering what was about to happen next, luckily these people would still have the sense of sound to help them get by day to day.
All of this cool information was presented in the book but few visuals or mini experiments were provided to help in my understanding of the material, this was the biggest downfall of the chapter. I was also wondering if we have access to the website for the book because it looks as if you can find many helpful examples on the website that is listed throughout each chapter. The two concepts that I am interested in learning more about are first and second order motion. I realize that they have to do with luminance and texture and how these concepts help us to grasp movement but I think it would be interesting to see a real world example of this. On a side note I was also wondering if astigmatism fits into this chapter because I know that motion and astigmatism are connected in some way.
Terms: apparent motion, Sigmund Exner, illusion, middle temporal lobe, neurons, color sensitive, Akinetopsia, neuropsychological, first level motion, second level motion, astigmatism, texture, and luminance.
Good post. I think akinetopsia would be much more difficult to live with than achromatopsia. A world without color would be confusing, but a world where you don't perceive motion is utterly dangerous. If you didn't see a car moving toward you, you would have to infer based on the snapshots you did get, that you should avoid it. This seems like an exhausting and metabolically costly process.
I didn’t find chapter 7 as enjoyable to read as some of the previous chapters, but still learned a lot about varying concepts. There were many interesting things to learn about, but I found a few things particularly interesting. I thought the concept of Motion Aftereffects (MAE) was important to understanding how our visual system perceives stationary and moving objects in the world around us. A motion aftereffect is the illusion of motion of a stationary object that occurs after prolonged exposure to a moving object. The existence of the motion aftereffects eludes to an opponent-process system like the process used in color vision. When humans see a stationary object, the responses of neurons tuned to different directions of motion are normally balanced. Neurons sensitive to upward motion fire at the same rate as neurons sensitive to downward motion, so these signals cancel each other out and no motion is perceived. An example used in the book was looking at a waterfall for awhile. IF you view a waterfall for a long amount of time, the downward motion-sensitive detectors become exhausted. Then if you switch your gaze to a stationary object, like a nearby rock, your neurons that are sensitive to upward-motion fire faster than the worn-our downward-sensitive neurons. Thus, we perceive the rocks to be drifting up. I thought the concept was interesting and the example was helpful because I have experienced this phenomenon before and now I understand why my eyes and brain perceived the stationary objects to be moving in that way.
I also found the physiology of the eye movements to be interesting because I have always enjoyed learning about the anatomy and physiology of the human body. There are six muscles attached to each eye, arranged in three pairs. These six muscles are controlled by an extensive network of structures in the brain. These brain structures can be stimulated through electrical signals, allowing the movements of the eye to be observed. The book used the example of stimulating a cell in the superior colliculus of a monkey. Upon stimulation, the monkey’s eyes will move a specific amount in a specific direction. Each time that particular cell is stimulated; the result of the eye movement will be the same, but stimulating an adjacent cell will render a different eye movement result. The superior colliculus also gets some input from the retinal ganglion cells. This input probably helps with the planning of eye movements. But, in response to stimulation of some of the cells in the frontal eye fields, the monkey will move its eyes to fixate a specific spot in space, and this is all dependent upon which direction the eyes are facing when the stimulation begins. It could result in the eyes moving up, down, left or right.
I found the concept of time to collision (TTC) interesting because I have been hit in the nose with a soccer ball and softball as a child, due to not being able to stop the imminent collision. I have often joked at my lack of hand-eye-coordination, and thought learning about what visual information we use to avoid or achieve collisions with approaching objects and our bodies was interesting. Surprising, despite humans’ distance judgment abilities, we are far better at judging time to collision than would be expected-well most of us, anyway. There is an alternative source of information in the optic flow that could signal TTC without the necessity of estimating either absolute distances or rates, known as tau. An example of how tau works is a ball coming toward one’s face, and the image on one’s retina growing larger as it approaches. The ratio of the retinal image size at any moment to the rate at which the image is expanding is tau, and TTC is proportional to tau. An advantage of using tau to estimate TTC is that it relies solely on information available directly from the retinal image. According to the textbook, all one has to do is track the visual angle subtended by the ball as it gets closer to one’s eye. It’s clear that animals and humans find estimating the time to imminent collision very important, and almost every species tested will attempt to avoid a simulated collision.
A concept I found the least interesting to learn about was biological motion. Biological motion is the pattern of movement of living beings, humans and animals. Gunnar Johnasson recognized that there may be something important about the motion of animals and humans that helps us identify the moving organism or object and its actions. The example used by the textbook was a photo or a tennis player. One can tell from the contours of his body that he’s in the act of moving to hit a tennis ball in the direction of his opponent. But a photo of the same tennis player in the dark with only the lights attached to his joints. In the dark photo, it is difficult to figure out what the pattern of lights is forming, and even that the pattern is of a human. But, when the lights on the joints of the dark photo are moving, one can decipher that it is a human and he is probably swinging an object to hit another object. I thought this was an important concept because I had never really considered this idea, but it wasn’t as interesting as learning about the physiology of eye movements, or how my visual system tries to avoid getting hit in the face with a soccer ball.
I think the concept of time to collision and tau will be the most useful to me in understanding sensation and perception, because being able to avoid getting hit in the face or body with a lethal object can be life-saving. In a less dramatic realm, being able to estimate the time to collision of any object approaching your body can simply result in avoiding injury or unwanted pain. Estimating time to collision can also help an organism achieve a desired collision, like hitting an object with a body part or another object. This can be beneficial in a variety of settings, like hitting a homerun in baseball, swatting a ping-pong ball before it lands in a red Solo cup, or deflecting a knife from making contact with your skin in an attack.
I would like more information about the concepts of optic array and biological motion. I understand that optic array is a term coined by J. J. Gibson to describe the collection of light rays that interact with objects in the world in the visual field of a viewer, and that some of these rays hit our retinas allowing us to see. I would like further details about this topic, or maybe a visual of the rays that hit our retinas and those that do not. I just don’t think this is enough information for me to fully understand what an optic array is or does, but maybe it’s a really simple concept that I’m over-thinking.
I would also like more information concerning biological motion, because I didn’t find it very interesting to read about, but maybe if I was provided with information concerning how it can help or hinder an organism’s chance at survival I would be more interested. I know biological motion is the pattern of movement of living beings, and I could understand how being able to recognize a moving object by its actions could be helpful in avoiding a predator or danger (like a falling rock).
Terms: motion aftereffects, MAE, opponent-process system, color vision, upward motion, downward motion, detectors, electrical signals, eye movements, superior colliculus, retinal ganglion cells, input, frontal eye fields, time to collision, TTC, imminent collisions, distance judgment abilities, optic flow, tau, retinal image, visual angle, biological motion, optic array, focus of expansion, FOE
First, have you seen the waterfall illusion? Second, do you think people like baseball players (for example) have incredibly efficient or accurate "tau processing"? It seems like they would. How would you test this? Third, I think biological motion is important because it can be differentiated by the brain from either apparent motion or artificial motion. This becomes important, as you mentioned, in those survival situations. As Gibson was all about, the visual system probably evolved to serve affordances and these affordances had a great deal of ecological benefits for us in our chaotic environment.
Many ideas and concepts in chapter 7 were interesting to me. I enjoyed the layout of this chapter and all of the information seemed to fit well together.
I found the concept of biological motion to be fascinating. I found this concept to be interesting because humans do not need much information to perceive that another human or animal is in motion. The two concepts that were most interesting to me about biological motion was how humans are able to detect human motion just by light. If the light is alone we are more likely to not perceive the object as human, but when the lights start to move we almost immediately perceive the motion to be a human. The second concept was how humans can detect motion between two individuals. If there motions are in sync we are more likely to know what activity they are doing, like dancing or fighting, when we know what one individual is doing we are more likely to know what the second individual is doing. When the motions of two individuals are not in sync in their motions it is harder for us to perceive what motion the two are in.
I also found the information about avoiding imminent collision to be interesting. This was interesting to me because within seconds we can detect if an object is coming towards us, and we can avoid the collision. This concept is known as the time to collision (TTC). The TTC is a mathematical calculation that calculates how fast we perceive or react to the collision (object coming at us). There is also one other way our optic flow can signal that there will be a collision or the TTC, and that is the tau. The tau can see that there will be a collision because our retina can detect when an object is getting closer to us (the object will get larger as it gets closer to us).
Another section I found to be interesting was the section about eye movements and reading. I found this section to be interesting because our eyes do this so quickly and we process the information so quickly. This is also something that is automatic for our visual perception, and we don’t really think about it. While people are reading their eyes are moving very fast. Reading involves us to fixate on the words. Also we must make succade, which is fast shifting of the eye from one spot to another; we have to do this while reading so the words reach our fovea. All of the information processing occurs while our eyes are in fixation. I also found it interesting that the English reading is asymmetrical, but the Hebrew reading is symmetrical (meaning they are opposite in the direction we are reading.) I found it interesting that people who read both can make the switch easily, but it is harder for someone who is not used to reading in the opposite direction.
I found the area about detection of global motion in area MT to be important in understanding sensation and perception. I found this to be important because most neurons in the MT (middle temporal lobe) are for motion and how we perceive motion. To detect visual motion we need to know the parts of the brain that are working when we perceive motion, and to understand sensation and perception we need to understand the parts of the brain, and what parts help us perceive motion.
Although I found the section about global motion in area MT to be important in understanding sensation and perception, I also found this section to be a bit uninteresting. The main reason I found this section to be uninteresting because it was a lot of information to take in. In this section there was a lot of terminology and I had to go back and re read so I would understand, and I still found some of the information to be challenging. I more than likely found this section to be uninteresting because it was also a section that was very important. I would like to understand more about how the parts of the brain work together for us to perceive motion.
After reading chapter 7 I would like to know more about the neurological disorder called okinetopsia. I would like to know more about how this disorder happens and how frequent this disorder is. I would also like to know if it is more likely to occur because of a traumatic event that affected the MT area in the brain, or because of a disruption in the cortical area of the MT, like drugs being used by the person. Another topic I would like to know more about is apparent motion. This is something I would like to know more about because I find it interesting that when you add many still pictures or drawings together you can perceive motion.
Terms: biological motion, imminent collision, succade, global motion, MT (middle temporal lobe), fovea, retina, okinetopsia, apparent motion, time to collision (TTC), tau
The most common route toward akinetopsia is definitely trauma to the brain (stroke, aneurysm, etc.) and probably not as often via experimental drug use. The apparent motion is pretty interesting and just shows you how important it is for the brain to be able to perceive and process motion. Since moving objects (real motion) in our environment could be a threat or benefit to us, it is beneficial to have a brain that assumes motion, even from stagnant images. The thing that is important to remember is that these primitive processing systems are always at work, even if they are not necessarily imperative to survival in our modern world.
In chapter 7 we were focusing on motion perception. A possible key component in the perception of motion is the middle temporal lobe or MT of our brain. If it does do what researchers believe it to do, then its key in all of the kinds of fashions that we perceive motions with. One of those things being apparent motion; meaning the illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession. I found this interesting due to as a fan of anime and animated pictures, it is really what I’m seeing when I’m watching it. These are stills of drawings or digitized drawings of images that are put into sequence to give the impression of movement. Much like those flip-books of pictures that as you flip through them they give off motion when in fact each image in station. The second thing I found interesting was second-order motion, the motion of an object that is defined by changes in contrast or texture but not by luminance. Second-order motion also involves texture or contrast defined objects, objects that are defined by changes in contrast or texture but not by luminance. The figure 7.9 gave a pretty good impression of the action without having to look at the web activity however; part of it is lost when not in motion. Amazing what can be seen out of some simple changes of contrast and texture can do to give the perception of motion. Another interesting thing I found was the biological motion, the pattern of movement of living beings. Us humans so used to movement in our lives ,that we don’t think much of it till we are forced to look at it for the sake of looking at it. I have seen the ‘dot walker’ and though there is nothing actually there to give an impression of activity and direction, we perceive it none the less. As if our minds are filling in the spaces with what we already know and the dots doing all the work.
The least interesting thing I found was perhaps was aperture problem. It seemed rather confusing for me, so I wasn’t able to understand it fully to be fully interested in it.
A thing I found most interesting and probably one of more important things in sensation and perceptions, knows where in our brain that our minds perceive the motions our eyes tell us. If the middle temporal lobe plays such an important part in our way of perceiving motion then without it, we would be in trouble. Much like apparent motion I think plays a key role in sensation and perception because though basic, it seems essential for our minds and eyes to be able to perceive that sort of thing in order to survive.
Topics I would further like to look into is the physiology and type of eye movements as such movements like smooth pursuit and saccade are key in our way to use our eyes to perceive our surroundings. I would also like to discuss akinetopsia, a rare neuropsychological disorder in which the affected individual has no perception of motion. Much like the woman in the video we saw in class, I find it interesting
Terms: akinetopisa, second-order motion, texture (contrast) defined objects, middle temporal lobe (MT), saccade, apparent motion, biological motion, smooth pursuit
A quick correction. MT refers to extrastriate cortex (still in the occipital cortex). MT extrastriate cortex is sometimes referred to as V5. Medial temporal lobes include things like the hippocampus, etc. So these areas of the brain are distinct. Damage to V5/MT would result in some form of akinetopsia (interesting condition where the subject can not perceive certain types of motion). Damgage to medial temporal lobes (MTL) would result in probably memory deficients depending on the locus of the damage.
Sorry you're right that it is Middle Temporal with respect to the visual cortex. Sorry I misread that.
The concept of motion is really explained well in the chapter and enlightened me on some pretty neat information I had never known. To simplify the explanation of motion and its value, one may define it as a dimension in perceptual activity that allows us to see where objects are going and where they will end up, which in turn, helps us to navigate throughout our environments. Motion can also have a deceitful perspective with regards to stationary objects. For example the image to start chapter seven, as seen on page 167, exemplify the illusion of movement. Illusions are false interpretations our brain leaves us to believe we see. The best example, and one of the greatest interests from the chapter, was the motion after effect (MAE). Motion after effect is best described in the chapter by visualizing a streaming waterfall surrounded by rocks. To visualize the stream of water rushing downward is motion. The rocks are stationary; they clearly are not moving or producing any kind of motion similar to the water flow. After visually witnessing this motion for an extended period of time, the rocks will appear to become the object of motion now, in an upward motion, one opposite of the actual downward motion of the water. The motion after effect is not the only illusory visual pertaining to motion, however. The term apparent motion also incorporates an illusion, and one that all of us have witnessed numerous times each and every single day. Apparent motion is defined as a smooth motion that is the result of extremely fast interchanges of objects which appear in different locations in swift succession. Most notably, this concept is seen through television or some sort of film. The images we see in cartoons appear unbelievably smooth in motion, such as the way the figures walk and move their limbs. Animation is produced from a vast variety of numerous still images that are shown at such high speed we are able to detect motion in a fluid way. Another thing I found interesting was the aperture. As humans we are able to clearly identify the movement of objects, whether it is up, down, left right, or diagonal. Apertures may provide a problem because they only show a portion of the object at view. This is also known as the aperture problem. Our V1 cells are unable to identify the direction of movement of an object because they have an aperture. There must be access to all components of these neurons, such as the global-motion detector, in order to accurately identify the true motion of direction. Another point of interest for me personally was reading about the idea of optic flow. In order to properly navigate ourselves around we must consider flow and motion information. Optic flow, a term coined by J.J. Gibson, is defined as “the changing angular positions of points in a perspective image that we experience as we move through the world”. When we are in high speed machines such as cars or on planes there is a specific destination point. This is known as the focus of expansion. To gather a specific idea of how this works the book illustrates a pilot’s ability to safely land a plane. While everything is in motion, the specific point of the landing strip will be stationary. Probably the most important section of the chapter that will help me in my understanding of sensation and perception is the eye movements and their physiology and different types, and specifically saccades. The eye is composed of attached muscles that are directed by the brain. Various brain structures are important for the stimulation of these muscles in order to produce desired function and movement of the eye. While there are involuntary movements of the eye, as well as many other body parts, there were three primary voluntary movements mentioned in the text. These three voluntary movements include: vergence, saccade, and reflexive eye movements. I am, however, most interested in the saccade movement. A saccade is the rapid eye movement from a fixation on one particular object to a different one. These saccades can be incredibly fast and up to to 1000 degrees per/s. Not including the REM sleep, the average person makes around 172,800 saccades per day! Shifting from a topic I found very interesting to my least favorite topic, I would have to say that smooth pursuit was the least interesting thing I read. It very well could be just because I only read, and not actually followed the mini experiments with the pencil and the black dot, that I found a somewhat lack of interest. There was also a couple terms that I will consider doing my Thursday assignment over. I would like to learn more information on the saccade movement because I also thought the section on saccadic suppression was very interesting. Also, since I find great interest in learning about abnormalities and unusual events, I would like to also find and learn more about akinetopsia. Akinetopsia is a disorder that affects individuals and they are unable to have any perception of motion. Since this entire chapter covers motion, I believe it would be very interesting to take a different angle on motion and learn why this disorder is present for certain people.
Terms: motion, illusion, MAE, apparent motion, aperture, aperture problem, focus of expansion, saccades, saccadic suppression, akinetopsia.
Good post. Seems like you learned a lot. Akinetopsia, from my knowledge, usually results from damage to V5/MT extrastriate cortex. Damage could be from stroke, aneurysm, tumor, etc. This damage to the neurons in this area of the brain will create a situation where the brain as the motion signals up to that point (MT) but once it gets there, no processing of the signals occurs since the neurons are damaged. Pretty devastating and dangerous condition to have.
Chapter 7 was a very interesting chapter and I learned quite a bit from reading it. Motion information is something that we use in our visual system to help us get around areas or places in our environment. J.J. Gibson coined the term optic array, which is the collection of light rays that interact with objects in the world in front of a viewer. Some of the rays will actually strike our retina, which in turn, enables us to see. Gibson also said that when we move through an environment we use something called optic flow. These are patterns that our visual system uses to determine where it is we are actually going. Furthermore, optic flow is the changing angular positions of points in a perspective image that we experience as we move through the world. The focus of expansion is something used in three-dimensional art when the artist is drawing a high school hallway, or a room. This term describes the point in the center of the horizon from which we are in motion, all points in the perspective image seem to emanate. This is one aspect of optic flow. Using the horizon line in a work of art, helps artist find and determine areas of the picture and placements of objects like hallways, bricks, homes etc. so that the illusion of flow or distance is accomplished.
TTC or time to collision is something that we use every day to avoid being injured. As humans we are far better at judging TTC than we are at determining TTC. Tau is an interesting concept as well that helps in the judgment of TTC. If someone were to throwing something at you, your retinas would begin to expand as the object got closer and closer. The rate at which the retinal image size at any moment to the rate at which the image is expanding is another way of explaining tau. Essentially because of time to collision, in cooperation with tau, humans and animals alike are able to judge the time of collision in any situation.
The movement of the eye, especially when you are reading a paragraph or chapter in a textbook is rather interesting. According to the book, when you are reading you are only fixating on the English words for a quarter of a second and then you are making a saccade of about seven to nine letter spaces. The purpose of making saccades is so that we can bring the information into our fovea, because print that is too far from are fovea is very difficult to read because of an issue with the texting being too crowded together. People that read English have a asymmetrical fixation and perception span. This means that when we are reading, we are able to gain information from up to fifteen English characters to the right but only three to four characters to the left. So it is proven that the asymmetrical is an attention factor and not a limitation of the visual system. Furthermore, informational processing only occurs during the actual fixation on the words, rather than when we are looking at our perceptual span.
The actual physiology and types of eye movements I found to be least interesting. I found this aversive because of the confusing Figure 7.15 in the book. When looking at the graph, it explains the six muscles that are attached to the eye that help it move. I just found this to be really confusing and I don’t think that it helped explain how we perceive movement in our visual world. This most important part of this section, I thought, was the section about the computation of visual motion. Figures 7.3, 7.5, and 7.6 in the book were exceptionally helpful in explaining this subject and pretty much help the full perception of a moving object. The movement of a ladybug (as explained in the book) are perceived by the firing of certain neurons with the mediation of certain neurons that measure the speed and position of the object to ensure the correct movement of the object or making sure that the ladybug is actually moving and not stationary. I would like to learn more about how we can use motion information on the subject of sensation and perception.
TERMS: optic array, optic flow, focus of expansion, TTC, time to collision, retina, tau, fovea, aversive, perception span, asymmetrical fixation
Good post. Optic flow is pretty interesting and we don't think about our world in this manner under normal states of consciousness. If you were constantly thinking analytically about your optic flow, it would be distracting. Luckily, the brain does this for us without much effort on our part. TTC and tau is pretty interesting to me. When I was a kid I played baseball and I was probably the worst person on our team. I am convinced that this has to do with tau and TTC (resolved in a terrible manner by perceptual/visual system). My tau processing was so bad that one time a ball was coming at me and instead of catching it, it hit me square on the nose causing a gush of blood. Needless to say, there's probably a reason I'm studying this stuff now instead of being an athelete.
Motion aftereffects are interesting phenomena in which stationary objects are perceived to be moving, usually due to prolonged exposure to the object. Typically, when an object is perceived there are several neurons that detect the motion of the objects. This phenomenon occurs when these neurons become off balanced due to fatigue. Thus, when there is an off balance then the motion is perceived differently because the neurons that are not tired will take charge of the perception. Motion aftereffects not only make stationary objects movable, but they can also cause objects to be perceived as going different directs. For example, if someone is staring at water coming out of a faucet they will first perceive the water as going down, but after a while the water will appear to be moving in an upward motion, this is because of motion aftereffects.
There are six muscles that are attached to the eye that control the eye movement. The muscles are separated into pairs: superior and inferior oblique (on the outside of the eye), the superior and inferior rectus (the muscles in the middle), and the medial and lateral rectus (the muscles at the back of the eye). The names of the muscles are determined by position on the eye. More specifically, superior means on the top of the eye and inferior means on the bottom. Each muscle is attached and communicated with different parts of the brain, I think of it as a form of mass communication throughout the brain. Each muscle not only connects to a different part of the brain, but it also controls a different form of eye movement. In addition to the muscles affecting eye movement, the superior colliculus is a structure important for initiating and guiding eye movements, as well as involuntary eye movements. This structure adjusts to different situations to determine the direct of the eye movement, which works with the motor system.
Before reading this chapter, I did not know that there were three types of voluntary eye movements: smooth-pursuit, vergence, and saccades. Smooth-pursuit is when the eyes follow the object is a swift, smooth motion. It is able to keep the focus of an object stationary, while other objects are moving. I wonder if this has to do with focus, and how our eyes focus on objects. I say this because I participated in the recommended exercise in the book to test my smooth-pursuit motion, and when I focused on the pencil, everything else in my visual field went slightly blurry. Vergence is most commonly used in instances concerning distance. This is how the eye adjusts to what it perceives, or in the case using convergence and divergence. Convergence is used when an object is close in the visual field and our eyes draw inward. Divergence is the opposite in that the eyes draw outward to maximize the visual field for objects farther away. Saccades detect speed of motion by rapid eye movement. It can focus on different objects quickly by changing the fixation point. What is interesting about this is that we can change our fixation point without realizing that we are doing so. We are capable of making three to four saccades in every second. Saccades is also how we perceive dreams when we sleep, because the eye is rapidly moving and thus images are formed to create dreams.
One thing that I found confusing about this chapter was the section about the neural circuit. I think it’s most confusing because the terms used to describe the process were letters rather than words. The letters tended to run together while I was reading it. After I read through the paragraph a few times, I feel like I understand the basic concept. Essentially, as an object moves across our visual field it must first enter one receptive field (Cell A) which will trigger a response (Cell X). The object will then cross the other receptive field (Cell B) which will then cause a similar response (Cell D). Cells D and X will then collaborate together to send the message to a different receptor (Cell M). Cell M in this case is the motion detector, so it is constantly firing. The motion detector is affected by velocity in the sense that it is sensitive to an object that is moving too fast or too slow, which it adjust to by having several detectors available.
I would like more information about smooth pursuit and how it works. I’m not sure that I fully understand how an object is perceived in a “smoother” fashion. I also found focus of expansion to be interesting, but I don’t understand it very well. I understand that it has to do with perceiving moving objects while one is moving, but after that I don’t grasp the concept.
Terms: motion aftereffects, neurons, perception, eye movement, superior oblique, inferior oblique, superior rectus, inferior rectus, lateral rectus, medial rectus, superior colliculus, involuntary eye movement, voluntary eye movement, motor system, smooth-pursuit, vergence, saccades, convergence, divergence, rapid eye movement, fixation point, visual field, neural circuit, receptive field, motion detector, velocity.
Good post. It is confusing when they use letters to describe neurons. I think the idea is that depending upon where in the visual field it is that you detect the object that is moving, that will trigger a motor command or another oculomotor command to cause a saccade to that are of space in front of you.
The role that the middle temporal lobe is believed to play in our perception of motion is the first thing that sticks out to me when I think back on the chapter. According to researchers this lobe is where the global motion detectors are held. A cool thing about the neurons here is that most of them are selective for only one direction. They also are not selective to form or color. It amazes me how specified neurons can be. All of these results like so much of the things we have learned about in this class so far came from research that was done on monkeys.
I also enjoyed reading and thinking about aperture. And aperture is an opening that allows you to only partially view and object. The problem with aperture is that when apparent motion is perceived it is hard to know exactly what direction the motion went in. When it is viewed like this a person may be wrong on which direction the object actually moved. The problem is with correspondence, it is hard to know which features go with one another. This is called the aperture problem. It is a problem because if the object had been viewed as a whole then there would be no mistake in its true motion. As
As an athlete the section on time to collision or TTC definitely stood out to me. The book talked about cricket and how fast the ball gets to the bat, and how humans judge things like this. Based on the research done by Lee there is information in optic flow that triggers TTC without the estimation of distances. Lee called it Tau. Tau works as an image coming towards you enlarges on your retina. The implication for increasing the survival rates of humans and animals using this are very great.
This was by far the best chapter for me to read the far. For the most part I was able to comprehend and follow what every section was discussion without much trouble. With that being said it was somewhat hard for me to find something that did not interest me. If I had to choose something the small section that talked about the muscles that control eye movement. I understand that there are six muscles in 3 different pairs. I am glad that the chapter did not spend much time on them though.
The most useful thing from this chapter for the understanding of sensation and perception is how motion is perceived. According to the research done motion is perceived my neurons that selectively pick up on directions. These neurons are located in the middle temporal lobe. Another useful thing to know about them is that they are not selective to anything else.
Although I like the information I read in the chapter about TTC I definitely would like to learn a little more about it. When I think of TTC I think about how vision and perception of motion effect hand eye coordination. I have also heard that some of the best baseball players have vision that is far better than normal so I think it would be interesting to research that.
The other area that I would like to learn more about has to do with using motion to navigate. In the book the example is used of a pilot trying to land a plane. I am not entirely sure what I would like to learn about this. I just think it would be interesting to research more on optic array, optic flow, and focus of expansion.
Key terms: aperture, apparent motion, TTC, correspondence problem, aperture problem, tau, optic array, optic flow, focus of expansion
Tau is pretty interesting. I like how you related this information to your experiences as an athelete. I think tau is absolutely relevant to atheletics and people with better tau processing are likely better at sports. How would you do an experiment to test this?
After reading chapter 7, I found many things to be interesting however there were three subjects I found to be very interesting. The first was subject of apparent motion. Apparent motioin is the illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession. Another subject I found to be very interesting was motion aftereffects. In order to understand motion aftereffects I had to learn some key terms first such as first-order motion. This is a type of motion of an object that is defined by changes in luminance. Second-order motion is the motion of an object that is defined by changes in contrast or texture, but not by luminance. A luminance-defined object is an object that is delineated by changes in reflected light. Another subject I found interesting is being able to use motion information to navigate. In order to do this we rely on something called optic array, optic flow and focus of expansion. An optic array is the collection of light rays that interact with objects in the world in front of a viewer. An optic flow is changing angular positions of points in a perspective image that we experience as we move through the world. Last but not least, the focus of expansion is the point in the center of the horizon from which, when we are in motion, for example running on the bike trail, all points in the perspective image seem to emanate. The final subject I found to be the most exciting for me was the physiology and type of eye movements. A saccade is a rapid movement of the eyes that changes fixation from one object or location to another. Another term I learned about was vergence, it’s a type of eye movement in which the two eyes move in opposite direction. This can be viewed as either both eyes turning towards the nose which is considered convergence, or away from the nose which is divergence. I personally am able to converge my eyes easily however I cannot diverge my eyes. I learned about what a reflexive eye movement was, it’s when the eyes move to compensate for head and body movement while maintaining fixation on a particular target. Adding to the physiology of the eye, I would like to add the physiology of the brain dealing with the eye. It has been determined that the middle temporal area is involved in the perception of global motion. After reading chapter 7, in general I learned that motion is a primary perceptual dimension and that it’s used to determine where objects are going and when they are going to get there as well as living our everyday lives without getting hurt by objects that could have possibly hit us. Something I didn’t enjoy as much in this chapter was the subject of akinetopsia. Akinetopsia is a rare neuropsychological disorder in which the affected individual has no perception of motion. It is caused by the disruptions to cortical area middle temporal area, otherwise known as MT. It’s not that I didn’t find this interesting because I did, it’s just unfortunate that this is a possibility for some people because motion perception is so important to us. Think about a deer having no motion perception, without it they would be super easy target because they would not be able to detect any movement from the hunter. With individuals that are diagnosed with this terrible disorder, they would have to watch out for objects flying at their head the rest of their life but not having the skills they need to avoid any injury. I think the two subjects that are most important when learning about motion perception is eye movements in general and also how using motion information to navigate throughout our world. If I had to choose two subjects that I could get more information on would probably be Tau and biological motion.
Terms: apparent motion. Motion aftereffects, luminance, first-order motion, second-order motion, luminance-defined object, optic array, optic flow, focus of expansion, saccade, vergence, convergence, divergence, middle temporal area, primary perceptual dimension, akinetopsia, tau, biological motion.
Tau is pretty interesting. See some of the above posts and replies for more information. I think the akinetopsia point you raised is important. People would have a difficult time getting around their environment. Good post about the different orders of motion.
I really enjoyed the section pertaining to apparent motion. After learning the physiological hierarchy behind motion detection, this concept seemed to follow very logically. This phenomenon was first demonstrated by Sigmund Exner, who set up a machine that generated a pair of separate sparks a short distance apart from each other. The apparatus was designed to alternate the sparks in such a way that they could be confused for a single spark moving laterally in one direction. As predicted, viewers actually thought the two sparks were a single entity since they appeared near each other in rapid succession. This also works with the “AND gate” theory developed by Barlow and Levick nearly a century later, since cells fire only when their adjacent inputs are stimulated. This is thought to occur regardless of any motion between these two points – the important thing is that the inputs are triggered in succession, which would imply directional motion.
Another cool portion was the discussion of time to collision. One of my very first sports memories involves pitching a tennis ball to my dad in the backyard and getting a “comebacker” right to the schnozz. Despite this potentially traumatizing experience, baseball is still my favorite sport to play, which is probably a big reason for me finding this section so interesting. Given my years of hitting experience, I would agree with the book’s argument that a mechanism must exist that goes beyond our less-than-ideal ability to judge depth and distance. I have been beaned a time or two in the batter’s box, and I have also successfully avoided such contact to the head, so there must be a way by which humans calculate TTC other than by using absolute distances. Several researchers have proposed using a ratio of the retinal image of the moving object as compared to the rate at which this image is expanding, otherwise known as tau. Relying on tau is a nifty little trick because the ratio is proportional to TTC and it can be calculated using only a series of retinal images. This hypothesis makes a lot of sense to me, but considering most species’ proficiency at avoiding hurtling objects I doubt this is the only means by which creatures calculate TTC, just the best one we have come up with so far.
And finally, I thought the part about saccadic suppression was also quite intriguing. Saccades are rapid, voluntary eye movements by which a viewer quickly changes their focus from one object to another. If we did not have firsthand experience with how our own vision worked, you would probably assume that we would become very disoriented at these times due to the “blur” effect similar to that which occurs whenever a live camera is moved around too quickly. However, our visual system is so well crafted that it circumvents this problem entirely by nearly shutting down entirely whenever saccades happen! As you may notice, this effect only occurs with rapid eye movement triggered by optic muscles and not when you move your entire head quickly or if you were to manually adjust the angle of an eye using your fingers.
A section that I did not find as interesting was the portion on akinetopsia – a condition where an individual is incapable of perceiving motion. This is probably just because it has become fairly routine to expect a discussion of individuals lacking in whatever ability we are discussing and not because the disorder is inherently boring or anything though. On the plus side, I found most of this chapter to be very engaging. A couple topics I would like to learn more about in class are eye movements as they relate to reading (perhaps we could even breach the topic of speed reading) and additional theories on time to motion.
Terms: apparent motion, “AND” gate theory, time to collison (TTC), tau, saccade, saccadic suppression, akinetopsia
My experiences with tau led me on a different path. A similar baseball experience happened to me when I was a kid and I remember thinking, "this is dangerous for someone like me who isn't very good". Now I understand completely why this was the case. It's probably all well and good for people with accurate tau, but not for me.
While reading Chapter 7, I found apparent motion, optic flow, and smooth pursuit to be the most interesting. Apparent motion has always been interesting to me because it is how cartoons and movies come to life. The most impressive (in my opinion) is Tim Burton’s The Nightmare Before Christmas. Every shot is actually a picture that was taken, the character or set is moved a fraction of an inch, and then another picture was taken. I remember watching the behind the scenes extras and they showed how they made Jack Skeleton talk. They had a bunch of his heads made and every single one had a different expression on it. Then, they would match up the head with what he was saying during a scene. A very long process but the finished product was amazing. I picked out smooth pursuit because it just reminded me of how you can make a pencil or pen look like it is made of rubber. You do this by holding it loosely between your index finger and your thumb ¼ of the way down the pen/pencil and then moving your hand up and down. I chose optic flow because I was having a lot of trouble with mine when I went to work. As I have said in previous blogs, I might be getting LASIC this summer. But before I jump under the knife I need to first see if I am a good candidate for LASIC. One of the requirements that I have to adhere to is that I have to not wear contacts before I go in. Contacts can change the shape of your cornea and I have to have mine in their natural shape to see if I can have the surgery. How all of this relates to optic flow is that I just got my glasses today and I feel like I am looking through a fun house mirror. How glasses and contacts change the image you see is different enough that if your eye is used to one method and then you switch to another you can get headaches and disoriented. As I was walking around, my focus of expansion was really giving me problems because the further something got into my peripheral vision the more warped it looked.
It’s not that I didn’t find it interesting, but the section on eye movements wasn’t all that interesting. Figure 7.15 kept bringing back memories of when my class had to dissect cow eyes in biology. I wasn’t grossed out or anything but it was just weird.
Biological motion, mostly because everyone uses it daily when they encounter or observe people and animals.
Superior colliculus and reflective eye movements.
Terms: optic flow, focus of expansion, smooth pursuit, apparent motion, peripheral vision, biological motion, superior colliculus and reflective eye movements.
Don't you mean "going under the lazer?" Anyway, I think you've got a good point about the difference in perception between using contacts versus eyeglasses. It seems different for a lot of people. For me, I'll stick with glasses since the idea of putting something on top of my eye disturbs me in a profound and neurotic way.
The two things in chapter seven i found interesting are aperture and correspondence problems. Aperture problem is the fact that when a moving object is viewed through a receptive field, the direction of motion of a local feature or part of the object may be uncertain. This is really cool and reminds me of the spinning tops that light up. I think we all probably had one but when you look at the lights on top you didn’t know which direction the top was spinning. That is a good example of what the aperture problem is.
The correspondence problem has something to do with motion detection. Is the top spinning left or is the top spinning right. Who knows? Well this correspondence “problem” is similar to the one we faced when studying binocular vision. There, the issue was which points on the left retina corresponded with which points on the right retina. As noted in the chapter on binocular vision, correspondence is only a problem for the researchers studying motion perception; as we will see, the visual system is remarkably adept at “solving” the problem. Like the D cell when it adapts quickly.
Even though we have to choose the not so interesting it is all somewhat interesting. So I chose the interocular transfer. Everything goes together so you can’t mention one thing about motion perception and not mention the other. Interocular transfer is the transfer of an effect from one eye to the other. We know that motion detection neurons must be located at some point at the beginning of the visual system, after information from the two eyes has been combined. Motion-sensitive cells are found as early as the striate cortex. This is where information from the two eyes is only partially integrated—hence the fact that the interocular MAE is not as strong as the MAE you experience if you view the stationary objects with the same eye that saw the moving objects. Information from striate cortex neurons is sent on to other areas of the brain, most notably the medial temporal (MT) lobe, for further processing.
And to continue on we will talk about how certain neurons in the brain are specialized for motion detection. Moreover, each motion-sensitive neuron is most responsive to a single direction of movement. Researchers believe that all of these direction-specific neurons are constantly firing in a sort of dynamic equilibrium. When you are viewing a stationary scene, the various neurons’ responses cancel each other out, so that no motion is perceived. If elements in the scene start moving, for example, to the right, neurons sensitive to rightward motion will increase their firing rate, leading to the perception of rightward motion. That is why MAE occurs.
In order for us to understand where Sigmund Exner and the other entire psychologist who are studying motion perception get all there information we would have to know all the small details about the visual system. Knowing these small details will help us in understanding the history of their psychology.
In class, I would like to learn more about the Computation of the visual motion. It talks about how to build a motion detector. It gives the definition of the word motion as something that change position overtime. Well apparent motion gives you the impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession. This has something to do with the computation of visual motion when they talk about the motion detection cells. They say M cannot simply add up excitatory inputs from A and B. So they have to add one named D. I know very confusing but D has a fast adaptation rate and works together with A and B. When working together the three connect with neuron X. M though is responding between A and B to make up lag. I need a detailed, visual view of what is going on here, I am a bit bewildered. It would be really cool to hear more about the different types of eye movements because you could probably tell us some great stories or show us some visual examples. Most of the eye movements we have all heard of like vergence which is a type of eye movement in which the two eyes move in opposite directions. When, for example, both eyes turn toward the nose or away from the nose. That is called convergence and divergence. When the eye is having rapid movements that change fixation from one object or location to another that is called saccade. Some movement can be automatic or involuntary which then is called reflexive eye movement. The eye is amazing and the more in-depth we get the better.
Terms: Computation of the visual motion, motion detector, apparent motion, correspondence problem, Aperture problem, MAE, Interocular transfer, Sigmund Exner, saccade, vergence, convergence, divergence, reflexive eye movement, retina
Just as a technical note. There is the middle temporal area (MT) of extrastriate cortex (motion) and the medial temporal lobes of the temporal lobes (memory stuff). It seems like you really got into this stuff, which is cool. Glad you enjoyed it.
I used to love going to restaurants as a kid and playing the games on kids menu's that asked you "to find the item that was different from all the others". Or where's waldo was a favorite for sure (loved the illustration in this chapter) and other books that had you using visual search. I found it really interesting to actually read about it in this chapter. Visual searches are an actual thing and psychologists, or whoever who make them have targets, distractors and set size* to make these puzzles. I would really like to do an experiment to see what my reaction time is, compared to an average. I also wonder why it is important for young children to do these things. Well, I am assuming it is important because visual search is found in children's books all the time. Is it to jog the brain and help it develop? This would be some interesting information to further research.
Secondly, I know Dr. Maclin has talked a little about how there is certain part of our brain that detects faces, but here we are learning it in this chapter. I found it very interesting that there is an actual part in our brain called the fusiform face area (FFA). Also, a new thing that I did not know was the parahippocampal place area (PPA), which is an specific area in our brain that detects images of places, like a house. This insane to me to think that there is one specific area on our brain that (for lack of a better term) lights up when we simply look at either face or a house, for example. Just another reason to be amazed by the human brain! Also, it is very interesting that when you put the two together, the FFA and PPA are both stimulated. I find it really interesting that when you look at a house your PPA fires, but when you look at a face, your PPA does not fire. While, the FFA fires strongly with a face stimulant, but still fires weakly when given a house stimulus.
I found the neglect visual-field defect very interesting. It blows my mind that one can literally just ignore something in their line of vision. At first, I thought that the neglect defect was simply blindness, but then the book described extinction and how Tipper and Behmann did the experiment of flipping the stimulus from the ipsilesion field to the contralesional field. The subject could always see the same stimulus. This is really interesting slash confusing. I understand that it is a very unique and not so prevalent disorder, but I would like to know more about it for sure.
One thing that I wasn't really into in this chapter was attending in time: RSVP* and attentional blink I am not sure if I really understood these or not. What I tried to understand, I really didn't care about. I think attentional blink is when you are focused on one thing, and you let another go in that time. Basically the name says it all. Not too interesting. RSVP was confusing and I'm not quite sure if I understand it.
The most important thing I read in whim of understanding sensation and perception would have to be the section on real-world searches, basic features guide visual search. This section helped me learn why things are categorized in certain ways. We have stuff like guided searches and conjunction search to help us out in the real world.
I would like to learn more about children and why there are so many visual search exorcises in kids books and work books.
Terms: visual search, guided search, conjunction search, target, distractor, set size, RSVP, attentional blink, fusiform face area (FFA), parahippocampal place area (PPA), visual-field defect, neglect, contralesional field, extinction, ipsilesional field.
I think you read ahead to the next chapter on attention instead of the perception of motion. BUT, that's fine, I like attention better anyway. I think the inherently fun thing about Where's Waldo is that you have to challenge yourself to overcome a capacity limited attentional system. It probably doesn't hurt to have kids doing visual search tasks (in moderation :)). But we perform visual search (implicitly) all the time. We constantly scan the house for our phone or our wallet or whatever. So, with RSVP, you're trying to capture the attentional blink. So, if you are scanning for a "P" there will be a number of other images or letters (depends on the task). You know the target ahead of time "P" so basically you just hit the space bar or button box when you see the "P". The letters/images are cycling through very very quickly (milliseconds) and the first instance of the "P" is easy to pick out. BUT if I show you another "P" right after the first target (P) occurs, you will miss the 2nd "P". WHY? Because you're attention has been devoted to searching for "P" and when it happens its as if it "refreshes" or takes a quick couple millisecond "break". The closer the second presentation of the target is to the first presentation of the target, more people miss it. Thus, RSVP is just hte task used to tease apart the attentional blink. There are many other versions of this task as well. It's sort of played out, but it can be a cool tool to modulate attentional load. Make more sense?
This chapter had a lot of good material that was very interesting. I had numerous things that I liked about it and apparent motion was one topic of interest. This concept was introduced by Sigmund Exner which he conducted an experiment that generated electrical sparks separated by a short distance and period of time. People would think that the spark was moving from one position to another. I found this interesting because this is how modern media is presented in today’s world. When we view a cartoon or a movie, what we are actually seeing is a bunch of pictures that shift frame by frame to create a moving object. The problem with apparent motion is that you have to see the whole picture in order for it to work. If you only have an aperture view than the motion will not work as it is intended from the whole view. This can lead to aperture failure, when a moving object viewed through an aperture confuses the receptive field which makes receptors perceive a movement the wrong way. To help correct this we have multiple V1 cells that perceive different parts of a moving object. These different parts are compared to each other to see if the movement is consistent each V1 cell. This was interesting to me because I was always curious on how we perceive cartoons and movies from a bunch of moving pictures.
Another topic I found interesting was Motion aftereffects. Motion aftereffects are the illusion of motion of a stationary object that occurs after prolonged exposure to a moving object. An example of this is staring at a waterfall for a while and then transferring your vision to the rocks beside it. The rocks look like they’re going up while the waterfall is going down. The book compared it to color aftereffects of chapter 5. When we look at a color for a prolonged period of time and then look away, we see the opposite color spectrum in our eyes from what the original color was. A cool experiment the book had was to close your left eye and keep your right eye open for 15 seconds. Then quickly open your left eye and close your right. You get a slightly reduced aftereffect from the right to left eye compared to what you would get with both eyes open. This is also called interocular transfer. I found this interesting because a lot of times I’ll be only looking through one eye when lying down. When I get up and switch eyes the whole picture I just saw looks slightly different. Now I know when that happens that I’m experiencing a motion aftereffect from a transfer of an image from one eye to another.
I found the section of using motion information to navigate also very interesting. The bit started out with J.J. Gibson who worked with the US Army on developing the theory of optic array. This is the collection of light rays that interact with objects in the world in front of a viewer. As we move through the environment these light rays change angular position which we use to determine where we are going. This is important for a pilot trying to land a plane. As we land our plane our optic array expands and we have to find the focus of expansion which is the point in the center of our view. This will be the landing strip in the example. The presence of optic flow means you are moving otherwise you would be stationary. By using optic flow we can determine our direction of heading by 1 to 2 degrees just by the pattern of optic flow.
The topic I found least interesting was that of computation of visual motion. In the section it basically talked about how motion detectors are created and how they work in our receptive field. It was really confusing to me because I didn’t really understand the whole concept of A and B neurons and why the D neuron had to be stimulated at the same time as the B neuron.
The thing that is going to be most beneficial to me that I read was probably the part about saccades. Saccades are a rapid movement of the eyes that changes fixation from one object or location to another. The part about when we read was most interesting to me. We make a saccade about every 7 to 9 letter spaces. You wouldn’t think that a simple task such as reading would require a large amount of eye movement. Another statistic I found interesting was that we produce 172,800 saccades a day. We even make saccades while we dream.
Two concepts I would like to learn more about would be second order motion and computation of visual motion.
Terms: apparent motion, aperture, aperture failure, V1, Motion aftereffects, color aftereffects, interocular transfer, optic array, optic flow, focus of expansion, neuron, saccades.
Smart people like Gibson working for the Dept. of Defense could be a really good or bad thing. He's got perhaps the most ecological account of perception and psychology, so it makes intuitive sense. Saccades are what gives rise to a lot of our visual abilities, which is why they are so interesting. That's a lot of computation for the brain and a lot of energy expenditure at the behest of the brain and sensory systems.
In chapter 7, the area that sparked my interest was the global motion area. In the visual cortex, the neurons may have much more information presented to it then the retinal cells, but they are still confined to a narrow area of the visual field. This is counterintuitive to motion, because in able to detect motion, you have to have access to bigger portions of the visual field. This problem is solved by having a global motion area in the brain. This area combines all of the motion information in the visual cortex and using it in perception. The global motion area is located in the middle temporal lobe of the cerebral cortex. The temporal cortex is also related to higher level visual processing.
Another area that interested me was the section about the optic array, or more specifically, optic flow. Optic flow is much like any kind of movement perception, except the individual is moving, and from our perception, the entire environment is moving. We use this ordered movement in our perception to tell us what direction we are moving and how fast we are moving. As a driver in a car, we usually have a single point of focus, or the focus of expansion. This area will always be stationary, and it is sensed by the fovea. The areas surrounding the focus of expansion move outward in your retinal image, and this is perceived as moving forward.
Another area that interested me was the section about biological motion. This is where animals are more tuned to perceive the movement of other animals. This ability seems highly developed by means of natural selection. The research done on this topic was very interesting and it is fascinating to me how we can discern characteristics from the movement of few stimuli.
The one area that I didn’t particularly like was the second-order motion section. It was not due to the subject material, but the way the material was presented. I could have been my mistake, but it seems that the author didn’t do a very good job of explaining second-order motion, and it is still confusing to me. For this matter, this is one area that I would be interested in learning more in class.
Terms: global motion area, visual cortex, visual field, middle temporal lobe, optic array, optic flow, focus of expansion, biological motion, second-order motion
I thought the text from chapter 8 was very interesting. In particular I liked the section on biological motion. Biological motion is when people are able to detect different patterns as living organisms. In the text they showed how that by placing small balls of light on a human being in a completely dark room, that people could tell by the shape of the item that it was a human. People were also able to detect the sex of the human based on the width of the shoulders and how the particular person moved. It is also easier for a the person in the dark in determining what the person with the light balls is doing when their is two people involved and they know what the first person is doing. However, I think that it would be very hard to determine what some moving balls of light are doing because there would be no focus of expansion point. There is no point that all the motion at which the balls of light around it move. For a person dancing, it would be their hips. So without knowing that it is a person, it would be very hard to understand what the balls of light are doing.
Another topic from the text that I found interesting was the time to collision. This is the amount of time an object in motion takes to hit a stationary object. An example of this would be how long a plane takes to crash into the ground. The most precise way to calculate this would be to know the speed of the plane and the distance from the group. However, there are many other variables that go into examples like this and it is hard for people to calculate things like this without instruments to help them. So, in examples that take split second decisions people use a thing called tau to figure out when the collision is going to happen. Tau is your brains estimate of when the collision is going to happen based on how quickly the object grows in your optic flow. So in the plane example, as the ground gets bigger in your optic flow, your body senses the collision will happen sooner and can estimate the time until collision. I thought this was interesting because when something is about to collide with you, you almost think that it is natural reaction or almost instinct. It is amazing that your eyes can communicate with your brain that fast and you can react without making a concious decision about it.
I also found it interesting that people who read English can concentrate up to 15 letters to the right of their fixation point, but only up to 4 of their left. People who read Hebrew (where you read right to left) have the opposite effect. And people who read both, can switch between the two. I thought this was interesting because it is seems remarkable that can alternate how they read based on what language they are reading.
I did not think the aperture problem was very interesting. The aperture problem is that when motion is viewed with certain discriminating things, it may not be able to detect motion, or at least direction of the motion. I thought that this was a rather obvious concept and was not needed.
Terms: biological motion, focus of expansion, time to collision, tau, optic flow, aperture problem
Chapter 7 was interesting as the focused on human sensation, attention and perception and recognized the fact that we do not have the brain capacity to process everything at once. Our attention is internal and external. Our internal attention applies to our ability to focus on a single point. External attention refers to how we perceive things around us.
Although the human brain is not able to process everything at once, our attention is overworked at most points in our lives. We are usually focused on more than one thing at a time. We may be reading, listening to the radio or the television at the same time, our attention is then divided into several directions and is not focused solely on one stimuli (overt attention), we may be reading and talking or looking at other people in the room and engage in covert attention. We rarely give our sustained attention to any one thing at a time.
Human perception is hard to understand. Although we are able to see many things at the same time, we are only able to process a couple of those things at a time. Our attention is usually drawn to a focal point and we are then able to process the stimuli in that focal area. Although we are only able to process a few things at this focal point, the human brain has a great memory capacity. I have experience this as I have travelled to different areas. I don’t always remember the street numbers, but I recall certain focal points of travel, and I am able to recover the correct route once I have gone somewhere. I don’t need a GPS, if I have been somewhere once; I am able to direct myself or someone else by memory. This is due to visual attention mechanisms that are able to focus on certain stimuli and is processed through motion and expansion in the visual field. It also ties into biological motion, where I am able to identify moving objects and actions as I am driving. This is interesting to me, because I know there are people who can drive somewhere once and never be able to get back without a map or GPS. Not everyone is focused on the same surroundings or focal points. Attention and perception is not the same for everyone—each individual is different in how we handle problem-solving issues and others may be able to visually process things at varying levels. I think the visual concept of estimating the time to collision is also important in driving, playing sports and everyday life. Without this we would always be hurt or in car accidents.
Some topics that I did not find interesting or may need more information about include the saccadic suppression and the comparator. The saccadic suppression seems complex as the visual system shuts down and suppresses information. The comparator area if the visual system receives a copy and another copy goes to the eye muscle. These motion signals and comparisons are a confusing part of the eye movement that needs a more in-depth explanation.
Terms: attention, perception, internal attention, external attention, overt, covert, divided, sustained and selective attention, visual field, focus of expansion, biological motion, time to collision, saccadic suppression, comparator.
Chapter 7- Taking action
After reading chapter 7 I really found the following three topics interesting; perceiving and moving through the environment, keeping balance, acting on objects- reaching and grasping.
Perceiving and moving through the environment section of the chapter was very interesting to me because this happens to me everyday. Once again I can relate to this topic because when we are walking, running, driving or any kind of movement we are always perceiving around us. Gibson stated that the optic array is structured by the surfaces, textures, in the environment and when we are moving it causes changes in the optic array. This is a great example of when we are standing still or sitting our view using the optic array of objects around us change when we are moving and perceiving the same objects. The optic flow is used when you are moving in a scene to perceive. Driving is a great example of an optic flow, when you are on a bridge you are going forward and looking at the end and the sides of the bridges are blurred and going the opposite direction you are moving. Moving and perceiving happens daily and it is easier to understand and be more observant now that I know these terms.
The second thing I found interesting is keeping balance. The importance of being able to see and perceive around us in our environment on a daily basis is to keep balance. When you close your eyes and stand on one foot (like I did as a demonstration) it is very hard to keep balance, and I have took advantage of that. The flow of balance is used in an experiment in the book by Lee and Aronson’s swinging room. The diagram shows when the wall swing toward the person they sway back to compensate. When the room swings away, the person sways forward. These examples show how balance and vision is used to take action in the natural environment.
The third topic I found interesting in this chapter is acting on objects- reaching and grasping. Gibson’s research shows that affordances is used to indicate what an object is used for. On a daily basis there are more “actions” then walking..etc, but we grab for things and pick up objects. When we are doing this everyday, we are wanting an outcome by that object we are reaching or grabbing for. The reason we may perceive or recognize an object is due to the objects function or (affordance). When we want to leave the house we reach for the doorknob and want to open the door so we can go outside, so we recognize the object and know its function.
The only thing I did not find interesting in this chapter was reading about is understanding the physiology parts of the brain for grabbing and reaching. The diagrams were helpful but once again, I looked up more pictures to understand the concept when I was reading to understand how the neurons respond to perceiving an object to reach or grab for it.
I think the most useful information in this chapter was learning to mirror others action in the brain. I thought it was interesting and useful to learn about mirror neurons that respond when we watch or observe someone else doing something and we perform the action after. We have seen the action done, and we now know how to perform the action.
The two topics I want to explore more information on is controlling movement with mind experiments on the computer and maybe even be in a study. The second topic I want to learn more on is Gibson’s study on affordance (objects function) and watch an experiment on this topic.
Chapter 7 in my book was titled Motion Perception. I truly loved this chapter because there were lots of illusions to look at and play tricks on my mind!
I liked learning about apparent motion. Apparent motion is when you see normal, smooth objects that look like they are moving. At first, I didn't quite understand what this meant but after further reading, I discovered that apparent motion is what is going on when you are watching an animated show! Each individual image is stationary but they are placed together with a slight difference to appear as if they are moving. I really liked this because I could relate it to everyday life. I would love to learn more about apparent motion in different ways than just animated TV shows.
I enjoyed learning about smooth pursuit and using the examples given in the book to understand. Smooth pursuit is when your eyes move in a smoother motion to follow moving objects. I did the experiment in which you draw a black dot on a piece of paper and roll a pencil just beneath it to show smooth motion in both the pencil and the black dot. Basically, smooth pursuit explains that even though your brain knows that the dot will not move, it still perceives movement because it has such a smooth gaze on the pencil which is moving.
One of the most interesting parts of this chapter was learning about akinetopsia which is a disorder in which the brain has no perception of motion. I didn't even know that this could be a thing until reading this chapter. Basically this means that you know an object moved, but you don't see the physical movement of the object, your eyes don't shift to follow the object. I really want to learn more about this disorder because it sparks my curiosity so I will be doing my topical blog on this subject.
I really didn't enjoy the part of the book when we started talking about what is working in the brain when certain motion perceptions are at work. I got very confused as to what they were talking about when using the middle temporal lobe or interocular transfer to explain. I know where the part of the brain are, but I am not all that good at knowing which part does what. I don't always understand the physiology behind eye movements and how it all comes into play. Yes, this would probably be most important to know but I don't exactly enjoy the biology in psychology. I think that I don't enjoy it because I don't always understand it.
Apparent Motion, Middle Temporal Lobe, Interocular Transfer, Smooth Pursuit, Akinetopsia