Chapter 1 notes
Chapter 1 notes Psyc4106W
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This 6 page Class Notes was uploaded by Jennifer Gittleman on Wednesday October 28, 2015. The Class Notes belongs to Psyc4106W at George Washington University taught by Dr. Philbeck in Fall 2015. Since its upload, it has received 37 views. For similar materials see Sensation and Perception in Psychlogy at George Washington University.
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Date Created: 10/28/15
l The Perceptual Process a Stimuli Steps 1 and 2 i Environmental stimulus 1 Tree that the person is observing 2 Perception of the tree is based on the light re ected from the tree ii Principle of transformation 1 Stimuli and responses created by stimuli are transformedchanged between the environmental stimulus and perception iii Nature of the re ected light depends on 1 Properties of the light energy hitting the tree midday sun overcast etc 2 Properties of the tree textures shape etc 3 Properties of the atmosphere air clear dusty foggy etc iv Eye s optical system 1 When re ected light reaches eye it s transformed as it s focused by eye s optical system a Cornea at front of eye b Lens directly behind cornea 2 If optics are working right they form a sharp image of the tree on the receptors of the retina 3 Retina 4 mm thick network of nerve cells that cover back of the eye and contain receptors for vision 4 If optics aren t working right they form a blurry image v Principle of representation 1 Everything a person perceives is based on representations of stimuli that are formed on the receptors and on activity in the nervous system b Receptor ProcessesTransduction Step 3 i Sensory receptors 1 Cells specialized to respond to environmental energy 2 Each sensory system s receptors respond to a speci c type of energy a Visual receptors respond to light b Auditory receptors respond to pressure changes in air c Touch receptors respond to pressure transmitted through skin d Smell and taste receptors respond to chemicals entering nose and mouth ii Visual receptors 1 Transform light energy into electrical energy because they contain visual pigment a Visual pigment lightsensitive chemical which reacts to light b Transduction transformation of one form of energy to another form crucial for perception because without it information of representation of tree wouldn t reach brain and perception wouldn t occur c Neural Processing Step 4 Network of neurons 1 Transmits signals from receptors through the retina to the brain and then within the brain 2 Changesprocesses these signals as they are transmitted Neural processing 1 Changes in these signals that occur as they are transmitted through the neurons 2 Processing continues the process of transformation Primary receiving area 1 Where electrical signals from each sense arrive in cerebral cortex a Cerebral cortex 2 mm thick layer that contains machinery for creating perceptions b Occipital lobe primary receiving area for vision c Temporal lobe primary receiving area for headng d Parietal lobe primary receiving area for skin senses touch temperature pain e Frontal lobe receives signals from all these senses and plays important role in perceptions d Behavioral Responses Steps 57 iv Perception step 5 1 Conscious awareness of the tree perceiving the tree Recognition step 6 1 Placing an object in a category that gives it meaning recognizing the tree Visual form agnosia 1 Inability to recognize objects Action step 7 1 lnvolves motor activities ex walking toward the tree e Knowledge iv Any information that the perceiver brings to a situation Can affect a number of steps in the perceptual process Can be information acquired a year ago orjust recently acquired Bottomup processing databased processing 1 Processing that s based on the stimuli reaching the receptors 2 Provide the starting point for perception v Topdown processing knowledgebased processing 1 Processing that s based on knowledge ll How to Approach the Study of Perception a Two approaches i Psychophysical approach psychophysics 1 Measures the relationship between the stimuli and the behavioral response 2 Example experiment where subjects were tested to see how well they could see the ne lines in stimuli that were presented at different orientations horizontal and vertical lines stimuli resulted in better detail vision behavioral response than the slanted lines a Oblique effect better detail vision for verticalhorizontal than slanted lines ii Physiological approach 1 Measures two relationships the relationship between stimuli and physiological responses and the relationship between physiological responses and behavioral responses 2 Helps understand the physiology behind the oblique effect 3 Example of measuring stimulusphysiology relationship for oblique effect a Coppola and coworkers presented lines with different orientations to ferrets using technique called optical brain imaging that measured activity over a large area of the ferret s visual cortex researchers found that horizontalvertical orientations stimuli caused larger brain responses physiological responses than slanted orientations b Example of measuring physiologyperception relationship for oblique effect i Furmanski and coworkers ii Human subjects brain activity was measured in a brain scanner while they carried out a task that involved detecting lines with different orientations experiment showed that the brain response physiological was larger when the subjects were detecting horizontals than when they were detecting slanted lines perception b Cognitive in uences on perception i How knowledge memories expectations that people bring to a situation in uence their perception 1 Starting place for topdown processing 2 Measure how knowledge and other factors affect all of the relationships lll Measuring Perception a Absolute threshold i Minimum stimulus intensity that can just be detected 1 Example for seeing a light the threshold would be the intensity at which the light can just barely be seen b Measuring thresholds i Classical psychophysical methods 1 Original methods used to measure the relationship between stimuli and perception 2 Methods of limits a Experimenter presents stimuli in either ascending order intensity is increased or descending order intensity is decreased 3 Method of adjustment a Stimulus intensity is either increased or decreased until the stimulus can just be detected b The observer adjusts the stimulus intensity continuously until they can barely detect the stimulus c Fast because observers can determine their threshold in a few trials by adjusting the intensity themselves 4 Method of constant stimuli a Experimenter presents ve to nine stimuli with different intensities in random order b Most accurate method because it involves many observations and stimuli are presented in random order minimizes how one trial can affect the next trial c Disadvantage is that it s timeconsuming ii Difference threshold 1 Minimum difference that must exist between two stimuli before we can tell the difference between them 2 Weber s law c Estimating magnitude i Magnitude estimation scaling 1 How we measure threshold perceptions 2 Experimenter presents a standard stimulus to the subject and assigns it a value they then present lights of different intensities the subject is asked to assign a number to each of these lights that is related to the brightness of the originalstandard light Response compression 1 The increase in perceived magnitude is smaller than the increase in stimulus intensity 2 Example you re inside reading a book and you look outside the window with daylight your eyes are receiving much more sunlight than they were reading the book but outside doesn t appear much brighter than the book because there is no danger iii Response expansion 1 As intensity is increased perceptual magnitude increases more than intensity 2 Example if you are receiving electric shocks very small increases in the shock cause large increases in pain the rapid increase in pain warns us there is danger iv Power functions 1 Steven s power law P KSquotn a Perceived magnitude P equals a constant K times the stimulus intensity S raised to a power n b Exponents less than 10 are associated with response compression c Exponents greater than 10 are associated with response expansion d Beyond thresholds and magnitudes i Phenomenological method 1 A person is asked to describe what he or she is perceiving or to indicate when a particular perception occurs a Can be at a basic level ex perceiving some objects as being farther away than others b An experiment may ask a person to name the color of a light or to indicate whether a taste is bitter or sweet 2 Usually used when testing the perception of people with brain damage a Describing noting what is seen heard felt etc b Recognizing naming the object ii Visual search 1 The observer s task is to nd one stimulus among many as quickly as possible a Example searching for a friend s face in a crowd 2 Measuring time the time between presentation of the stimulus and the observer s response to the stimulus
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