Cognitive Psychology 2101 Week 3 Notes (9/15)
Cognitive Psychology 2101 Week 3 Notes (9/15) PSY 2101 - 001
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This 5 page Class Notes was uploaded by Asmaa Abdullah on Friday September 16, 2016. The Class Notes belongs to PSY 2101 - 001 at Temple University taught by Pamela J. Shapiro (P) in Fall 2016. Since its upload, it has received 17 views. For similar materials see FOUNDATIONS OF COGNITIVE PSYCHOLOGY in Psychology (PSYC) at Temple University.
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Date Created: 09/16/16
9/13: Exam 1 (Hope you did well!) 9/15: Chapter 3: Visual Perception The Visual System ● visual perception seems easy and effortless ○ Fast ○ automatic ● while we actually undergo complex cognitive mechanisms to perceive the world around us ● Vision is the modality through which much of our knowledge is acquired ● Vision provides an excellent illustration of how the close study of the brain can proceed and what it can teach us. ● Neural bases of vision well understood What can we learn from brain damage? ● Akinetopsia ○ Inability to perceive motion ■ See “nothing between” location ■ (imagine it like the comparison between comic books and movies) ■ we take motion perception for granted ○ L.M. a 43 year old woman with bilateral lesions to the temporo occipital cortex ■ She feared crossing the street ■ Had trouble following conversations ■ couldn’t pour tea Structure of Visual System ● is designed to project a sharp image onto the retina ○ Light enters the eye through the cornea ○ The cornea and lens refract the light rays to the retina ● Retina has three main layers ○ Rods and cones ○ Bipolar cells ○ Ganglion cells the optic nerve ● Photoreceptors ● Rods Cones Lower sensitivity Higher sensitivity Lower acuity Higher acuity Colorblind colorsensitive Periphery of the retina In the fovea ● A series of neurons communicates information from the retina to the cortex, each layer stimulating the next ○ in the eye ■ photoreceptors ■ bipolar cells ■ Ganglion cells and the optic nerve ○ In the thalamus: ■ Lateral geniculate nucleus (LGN) ○ In the cortex: ■ V1 ● the primary visual projection area (primary visual cortex) located in the occipital lobe ● Different neurons in area V1 are specialized ● resulting in parallel processing, not serial processing ○ Complex process can be split up and worked on by different areas. ○ Then these different processing streams can be quickly integrated. ○ In parallel processing, one process does not have to wait for the other. It’s much FASTER ○ from area v1, info is sent to many secondary cortical visual areas for further parallel processing ○ These secondary visual areas lead to two major processing streams, the what system and the where system. The what system: ● Identification of objects ● Occipitaltemporal pathway ● Damage Visual agnosia (inability to recognize objects) The where system: ● locations of objects and guiding our responses ● Occipitalparietal pathway ● Damage problems with reaching for seen objects ((Different aspects of a single objectshape, color, movement, locationare analyzed in different parts of the visual system)) ● Parallel processing splits up problem → but we do not see the world as disjointed → binding problem Elements that help solve the binding problem ● Spatial position—features are mapped to location ○ visual areas processing features like shape, color, and motion each know the spatial position of the object ● Neural synchrony—cells fire together ((Cells that fire together, wire together)) ○ visual areas processing features of the same object fire in a synchronous rhythm with each other Attention is critical for binding visual features. ● When attention is overloaded, people will make conjunction errors. ○ correctly detect the features present on a visual display, ○ make errors about how the features are bound together, ● People with attention deficits due to parietal cortex damage are particularly impaired at judging features combined into objects. ● An account of vision requires both lowerlevel activities and higherlevel activities ● Lowerlevel ○ Singlecell recording ■ Frequency of action potentials = various visual stimuli ■ The more frequent the neuron’s firing rate → neuron is specialized for the certain stimuli that causes the frequent action potentials ● Researchers manipulate stimuli and record which stimuli triggers what neurons ● This is how they map out the receptive field for visual system’s cells ○ Receptive fields of bipolar cells, ganglion cells, and cells in the LGN have a centersurround organization ■ stimulu s in center leads to faster firing rates ■ stimulu s in surrounding area leads to slower firing rates ■ the closer you get to the sensitive area, the more frequent the action potentials ○ Receptive fields of cells in the primary visual cortex (V1)are lines of particular orientations Form Perception ● The process through which the basic shape and size of an object are seen ● Object recognition is the process through which the object is identified ○ Begins with the detection of simple visual features ○ Our perception of the visual world goes “beyond the information given” ○ Gestalt psychology: “The whole is different from the sum of its parts.” ■ If an object can be perceived in different ways, only one way is perceived at a time. ■ No more than one perception is possible at the same time ■ Figure/ground organization and Necker cube are examples of this ■ These examples might suggest that perception proceeds in two stages: ● One where visual features are processed ● And a later stage in which perception goes “beyond the information given.” ■ However, this view presumes serial processing, not the parallel processing that characterizes the visual system ■ Brain areas that analyze basic visual features and the brain areas that analyze largescale form are interactive, each sending information to the other ● This is another example of parallel processing ○ What we see is not just determined by the stimuli in front of our eyes, but also the brain’s interpretation of that stimulus ○ the perceptual system operates as if it were generating hypotheses about what objects are being perceived, given the available data ● Your ability to interpret forms is governed by a few basic principles ○ Similarity: We tend to group things that have similar features ○ Proximity: We tend to group things that are close together. ○ Good continuation: We tend to see a continuous form rather than broken or multiple forms. ○ Closure: We tend to perceive closed figures rather than incomplete ones. ○ Simplicity: We tend to interpret a form in the simplest way possible. ● The sensory information we receive changes but object properties appear as constant. ● Perceptual constancy ○ Size constancy ○ Shape constancy ○ Brightness constancy ● We need to know distance to be successful at size, shape, and brightness judgments ● Perceptual Constancy and Unconscious Inference ○ distance cues to judge size (unconscious calculations) ○ relationships and proportions ○ ((Closer objects cast larger retinal images and vice versa)) ● Binocular disparity ○ Each eye receives different stimuli. ○ The difference in the distance between object A and B on each retina, allows us to perceive depth. ○ This is why we have a different perspective from each eye
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