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lecture 21.doc

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University of Toronto Scarborough
Steve Joordens

Psychology-Lecture 21- Chapter 7 (chapter 6 in textbook) Perception - Sensation vs Perception - Sensation is the raw energy sensory process of that refered to as bottom up processing. Works its way up into higher processes. - Perception is due to all things such as context, your experiences, your past, etc. -Vision- there a signal sent from the retina to the ocipital lobe - the retina, photoreceptors are not evenly distributed. (cones in the center, rods on the around that) - cortex- alot more brain to the retina (middle of the retina) - primary sensory cortex is also related to the fovea. - visual fields: every (nerve) cell in the brain has a part in the brain that it responds to. - feature detector cells: the cells become excited when they see specific lines (eg: horizontal, vertical, different angles) - Secondary cortex-collection of features and colours that are rep. in different parts of the visual field (where) - the latter part of the brain, the association cortex puts the features together, compares it to memory, and figures out what we are looking at --> perception - perception is the categorized result of sensation - Damage to the primary visual cortex-blind spots - achromatopsia- inability to see colour - damage to one side of the association cortex causes this inability to see colour- only able to see changes in brightness- the colour information gets lost and does not get integrated in the recognition of the object - schitoma (blind spots)- damage to primary association cortex affects that causes holes in the visual field - damage to other parts of association cortex can cause an inability to perceive motion (just see snapshots of time not fluid motion) - parietal region of visual association cortex is damaged: during information processes, the border areas (eg border between occipital and parietal region) become regions where things are being integrated - visual agnosia- people can see things but they cant tell you what its used for. - Prosopagnosia- a little part at the back of the brain called the fusiform gyrus which is important for perceiving things as a whole (e.g. faces) This problem causes people to not be able to recognize the person from just their face but they can recognize the face. - There is another type of people who can see and recognize a person, but they dont feel familiarity towards them. Basic Issues-Figure vs. Ground - Figuring out where an object starts and stops called figure vs ground - This would be important for artificial intelligence because it would be handy if they could tell the difference between the object it is looking for and the background Basic Issues-Perspective - Context also has to do with how you see things (eg after hearing a story of a old woman then you will probably see a old woman) - This is a good example of sensation vs perspective- you see the same thing but your interpretation of the image is what is changing. Other Reversible Figures - Necker cube example Psychology-Lecture 22- chapter 7- Perception- (chapter 6 in text)-continued... Slide 11: Gestalt Laws of Grouping - Weber- working with the weights, lights and how it is represented in the mind - Kind of perception - Gestalt means the whole is more than the sum of its parts Slide 12: Demonstration of the Importance of Objects over elements - When you have a object made from elements, the object usually takes precedence over the object, the object is perceived over the element - Globally- the object - Locally the element - In an experiment where people have to look at objects (made of elements) and they have to identify the object (eg what letter it is) it is found that if they identify the letter of the object, it is quite easily done (so local doesnt really interfere with the global) but if they have to identify the local (letter) over the global, then they have a bit more difficulty. Slide 13- Law of Proximity - Close things tend to be grouped together Slide 14- Law of Similarity - Items that look similar (eg same colour) tend to be seen as the same form Slide 15- the Law of Good Continuation - People like when things continue - Even if you cant see part of something, you assume that it is continuous across (eg: when someone is standing behind an object and only their legs and head are visible, you still assume they are connected and not that there is a hole in between. - We can kind figure what is missing if something isnt there Slide 16- the Law of Closure - - In this image, you might see a triangle on top of a triangle and 3 circles but actually, there is no triangle there, the mind just makes imaginary boundaries that seem like its there to make a complete image Slide 18- the Law of Common Fate - While looking for an animal in a tree that is camouflaged, you will not be able to see it but as soon as it moves, you can notice exactly where it is and what it looks like. - This is because, obviously, motion attracts the vision, but also, because the body moves as a whole so it shares the same fate. - Features that cannot be seen dont seem to be bound together, but once they start moving together, they seem to be bound together (with a common fate) Slide 23- Perception of form-Summary - The goal of perception is to identify the OBJECT (not the things that make up the object) Slide 24- Figuring out what the objects are - Gestalt psychologist spent a lot of time figuring these things out. - Our mind fills in the necessary missing parts to make the object look whole. Slide 25- Templates and Prototypes - One idea of how humans have the ability to recognize an object is the reverse cookie cutter idea- if you have cookies and labelled cookie cutters but you dont know the shape of the cookie, you can take the cookie and see which cookie cutter fits and from there you can know what shape it is. - The problem with that is that, sometimes (for example, dogs) there are many different types of the same thing and different angles that they can be viewed from so you would need a whole lot of cookie cutters or templates to identify the same object. - A better idea of this is the notion of a fuzzy template or a prototype- you have an idea of what the average, for example dog, would look like. Slide 26- Evidence Supporting Prototypes - For example: if you asked someone to press a button every time they saw a bird an you showed them these pictures, when they see the image of the stereotypical bird, they will recognize it quickly, but of you showed them a picture of a rooster, they will take a bit longer, and then a penguin even more longer. - This also has to do with your cultural experiences what is a common bird for you Slide 27- Recognition of Distinctive Features - For example: in the mail office, human were the ones who had to sort the mail but then they decided that it would be more efficient if computers did that job. The only problem was that computers could not recognize the writing of different humans (hand written addresses). So they created the system of the postal code. This made it easier for the computer to recognize the letters and numbers. - They did this by making the computer recognize line positions (eg horizontal, vertical, diagonal) of the letters rather than the letter itself. Slide 28- GAME-Lets spot the Z - In this game, in the first set of letters, the Z is much easier to find because all those letters are curved not straight - In the second set of letters, the Z is much harder to find because all the letters are made of horizontal and diagonal lines Slide 31-Distinctive Features and Real World Objects - Geons- basic three dimension features - This feature is also perceived the same way as 2D features Psychology- Lecture 23- Chapter 7 Perception continued... (text chapter 6) Slide 32- Help from Context - Bottom-up=sensation from the world to the brain - Top-down= the brain top operating and processing the information before we can perceive it and it has a bias because of memory and that is what you see because we want it to make sense with what we know (through memory) Slide 33- Perception of Objects- Summary - Context plays a big role Slide 35- Special Information - How do you know where things are- spatial location - What conscious perception - Where- not conscious Slide 36- Depth Perception - Where = the depth perception - Why do we have/ need two eyes? - The reason is depth perception Slide 37- Binocular Cues-Convergence - Binocular Cues- getting information with two eyes - As something comes closer, the eye turns in and if something is farther, the eye moves outward. The muscle in charge of this action is attached to the brain and by knowing the angle at which the eyes are turned (how far or how close the eyes are), the brain can figure out the distance of the object from the person. - This is mostly to do with the spatial position of the object Slide 38-Retinal Disparity - What youre not looking at - The stuff around the object that you are focusing or looking at - When you look at an object, anything behind the object will look doubled and the farther it is behind the object you are looking at, the farther apart the doubles will be. Slide 39-Monocular Cues-Interposition - The object you see more of is usually in the front Slide 40- Monocular Cues- Perspective - Eg. When tossing a ball: as the ball comes closer, it gets bigger or takes up more space within the retina. As it gets farth
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