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January 19th.docx

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University of Toronto St. George
Adam Keith Anderson

January 19 , 2012 What’s Perception For? - Evolutionary adaptionist view  Shaped by environment to optimize fitness  Differences in animal perception  Humans: visual animal – human depends on visions so much that other senses are neglected, the same does not apply to animals  Dogs: olfactory sensitivity (―smell face‖)  Bat ―vision‖  Bird brains: Magnetic fields - What do they help us do?  Perceptual toolbox  Work with environment  What is perception for?  What's the problem to be solved? Perception: the way we think of the Sensation: world/knowledgethe peripheral devices bringing working of the brain input into our central - The central processing unit nervous system (CPU) - Receptors: little specialized - Consciousness happens "peripherals" when sensory receptors pick up information processed by - Retina: Does your retina see? the brain and interacts them - Relatively hardwires with experience - Influence of knowledge, learning There is not a clear distinction between sensation & perceptionWhere does one beings and the other ends? The Perceptual Process: - The person is always a part of the perceptual experience I. Stimulus: what is out there in the environment, what we actually pay attention to, and what stimulates our receptors - Exists in the environment and within our body  Environmental stimulus: all things in the environment that we can potentially perceive (the surroundings)  Attended stimulus: the subject of a person’s attention; changes from moment to moment as the person’s attention shifts (the moth)  Stimulus on the receptor: formation of a representation of the attended stimulus on the receptor (image of the moth on the retina) - Perception does not start with the stimulus  When a tree falls and there’s no one thereno soundno perception  Sound does not exist outside of our brain. It is the interaction of the physical stimulus and the brain that produces perception. Physical energy ≠ perception. The stimulus must fall on a receptor in order for perception to take place. - We don’t perceive what’s on receptors  Ex. the image on our retina is always inverted even though we don’t see the world upside downwe do not see the world the way it is presented in the retina II. Electricity: the electrical signals that are created by the receptors and transmitted to the brain - Sensory transduction: transformation of one form of energy to another  Nervous system: energy in the environment (Ex. light energy, mechanical pressure, chemical energy) is transformed into electrical energy.  Retina: lightchemicalelectrical  Touch: physical compressionelectrical - Transmission: electrical signals activate other neurons, which in turn activate more neuronssignals transmitted to the brain  If the signals don’t reach the brainno perception - Neural processing: involves interactions between neurons  Processing: changes the input into something else  Deals with electrical energy and the action potential  Starts at the central nervous system (retinal photoreceptors are not nerves)  Periphery (Ex. retina) vs. Brain (PNS (sensory nerves) & CNS (Axons))  Neurons in the brain are organized into a road map; most are two directional  There are billions of neurons and each has around 1000 connections  No random connections  Controls the flow of information III. Experience and Action: our goal—to perceive, recognize, and react to the stimuli - Perception: transformation of electrical information into perceptual experience; ―conscious‖ sensory experience?  Unconscious sensory experience:  Subception (1940-50s): processing of emotionally significant information unconsciously  Bottom-up/data-based processing: from the world up to our brains  Top-down/knowledge-based processing: what you know about the world interferes with/guides the perceptual process; the brain makes educated guesses about what you are perceiving  Brain is not Tabula rasa  Knowledge is ―higher-order‖, receptors ―lower-order‖  Cup: 1) A block placed vertically onto the cup: computer can recognize it as a coffee cup based on how things in the physical world works (Gestalt grouping: good continuation)no knowledge requiredBottom-Up 2) A block placed diagonally onto the cup: computer cannot fill in the missing information because it is against how things work in the physical worldneeds prior knowledgeTop-Down  Much more than the stimulus, it is a constructive process; the brain perceives based on what you know - Recognition: ability to place an object into a category that gives it meaning; perception’s contact with meaning  Can you perceive without knowing? 1. Visual Agnosia: ―vision‖ without knowledge; intact vision but object blind  They can report on their perceptual experience but they do not have access to knowledgethe order they draw the picture is different from someone without brain damage  Lower level perceptual processes intact 2. Modularity/informational encapsulation/cognitive impenetrability  Do you have to think to breathe, have your heart beat? Certain bottom-up processes are not influenced by knowledge  Cognitive impenetrability  Visual illusions still occur despite knowing they are illusions (Muller-Lyer illusion)  It’s almost impossible to not use your knowledgecan’t ask you to not recognize a word and just process color, orientation of lines  Stroop Effect: Latent response when the content of the word contradicts with its physical property  Knowledge can irrevocably change the process of perception  Where do top-down processing influences on perception starts?  There are limit to top-down perception (ex. imagination of a steak does not create an image of it on your retina, it occurs at some higher/later stages in your brain)  Recognition without perception? Access knowledge without perceptual awareness
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