Chapter 5 notes
Chapter 5 notes Psyc4106W
Popular in Sensation and Perception
Popular in Psychlogy
This 5 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 13 views. For similar materials see Sensation and Perception in Psychlogy at George Washington University.
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Date Created: 10/28/15
Why is it so Difficult to Design a Perceiving Machine a The Stimulus on the Receptors is Ambiguous i Inverse projection problem task of determining the object responsible for a particular image on the retina an image on the retina can be created by many different objects in the environment therefore the image on the retina is ambiguous b Objects can be Hidden or Blurred i Problem of hidden objects occurs any time one object obscures part of another object people understand that part of an object that is covered continues to exist ii People are also able to recognize objects that are blurry while computers cannot c Objects Look Different from Different Viewpoints i Viewpoint invariance ability to recognize an object seen from different viewpoints ll Perceptual Organization a Perceptual organization the process by which elements in the environment become perceptually grouped to create out perception of objects involves two components grouping and segregation i Grouping the process by which visual events are put together into units or objects Dalmatian example ii Segregation the process of separating one area or object from another b The Gestalt Approach to Perceptual Grouping i Gestalt psychologists quothow are con gurations formed from smaller elementsquot Structuralism 1 Distinguished between sensations and perceptions 2 Sensations combine to create complex perceptions and can be aided by the observer s past experiences 3 Gestalt psychologists rejected this idea Apparent Movement 1 Although movement is perceived nothing is actually moving illusion 2 One light ashes then a short period of darkness then another light ashes in a different position ex stock ticker sign 3 Whole is different than the sum of its parts iv Illusory Contours 1 Another demonstration that argues against sensations and agrees that the whole is different than the sum of its parts 2 No physical edges present Pac Man example c Gestalt Organizing Principles Organizing principles determine how elements in a scene become grouped together the starting points for these principles are things that usually occur in the environment 1 Good continuation points that when connected result in the lines looking like a smooth path ex two wires objects that are partially covered by other objects are seen as continuing behind the covering object ex rope 2 Pragnanz every stimulus pattern is seen in such a way that the resulting structure is as simple as possible ex Olympic symbol 3 Similarity similar things appear to be grouped together which could be caused by shape size or orientation ex dots 4 Proximity nearness things that are near each other appear to be grouped together ex candles 5 Common Fate things that are moving in the same direction appear to be grouped together ex ock of birds ying together 6 Common Region elements that are within the same region of space appear to be grouped together ex circles in ovals 7 Uniform Connectedness a connected region of the same visual properties color texture motion is perceived as a single unit overpowers proximity ex circles connected together by line d Perceptual Segregation Perceptual segregation the perceptual separation of one object from another Figureground segregation what causes perceptual segregation Figure separate object that stands out from its background ground Properties of gure and ground 1 Reversible gureground can be perceived either as two dark blue faces looking at each other in front of a gray background or a a gray vase on a dark blue background 2 Border ownership property of the border belonging to one area Imagebased factors determine which area is gure 1 Areas lower in the eld of view are more likely to be perceived as gure but left and right orientation does not affect it red and green areas vi 2 Figures are more likely to be perceived on the borders that bulge out in large scenes red square on gure Subjective factors that determine which area is gure 1 Wertheimer W and M one picture shows the two look like letters and the other picture shows the two look like an image because of the principle of good continuation and overrides effects of past expedences 2 Gibson and Peterson thought gureground formation can be affected by meaningfulness of a stimulus woman gure in black looks like the gure but when she is ipped upside down they did not say the black part was the gure lll Perceiving Scenes and Objects in Scenes a Scene a view of realworld environment that contains background elements and multiple objects that are organized in a meaningful way Objects are compact and acted upon Scenes are extended in space and acted within b Perceiving the Gist of a Scene Gist of a scene scenes are large and complex but you can identify most scenes after viewing them for only a fraction of a second ex ipping through channels on the TV Mary Potter study showed observers a target picture and asked them if they saw that picture in a sequence of 16 rapidly presented pictures accuracy was almost 100 even when the pictures were ashed for a quarter of a second even when the target picture was speci ed with a written description observers accuracy was almost 90 FeiFei experiment presented pictures of scenes ranging from 27 ms to 500 ms and asked observers what they saw used masking to make sure observers saw the pictures for exactly the desired duration Oliva and Torralba global image features enables observers to perceive the gist of a scene rapidly through certain features 1 Degree of naturalness natural scenes have textured zones and manmade scenes have straight lines 2 Degree of openness open scenes with a visible horizontal line and few objects such as the ocean while forest scene is not open 3 Degree of roughness smooth scenes such as the ocean vs rough scenes such as the forest 4 Degree of expansion convergence of parallel lines such as looking down railroad tracks that vanish in the distance 5 Color characteristic colors such as an ocean scene blue and the forest green and brown c Regularities in the Environment Information for Perceiving i Regularities in the environment characteristics of the environment which occur frequently and are effected by our past experiences ii Physical regularities 1 Regularly occurring physical properties of the environment a There are more horizontal and vertical lines in the environment than angled lines so people can perceive horizontal and vertical lines the best b Objects in the environment have the same colors so if the color changes that usually means we are looking at a different object c Lightfromabove assumption indentations in sand iii Semantic regularities 1 When we think about certain objects we associate them with their characteristics in a scene a When we think of an office we usually think of a desk with a computer on it and a chair d The Role of Inference in Perception Helmholtz i Theory of unconscious inference our perceptions of things are based off of our unconscious assumptions ex blue rectangle and red rectangle ii Likelihood principle we perceive the object that is most likely to have caused that pattern based on our past experience ex blue rectangle perceived to be in front of red rectangle iii Bayesian inference takes probabilities into account for inferential perception IV Connecting Neural Activity and Object Perception a Brain Activity and Identifying a Picture i Kalanit GrillSpector interesting in determining the relationship between the brain activation that occurs when looking at an object and the person s ability to identify that object presented pictures of Harrison Ford s face to 50 ms and observed their neuron activity when the person correctly identi ed his face there was large neuron activity when the person incorrectly identi ed his face there was a medium amount of neuron activity when the person saw nothing there was little neuron activity b Brain Activity and Seeing Binocular rivalry occurs when the observer perceives either the lefteye image or the righteye image but not at the same time 1 Tong et al colored glasses caused the picture of person s face to left eye and house to right eye observers perceived just the face or just the house back and forth subjects pushed one button when they perceived the house and another button when they perceived the face used fMRl to measure subject s PPA and FFA activity increased in PPA when perceiving the house and activity increased in FFA when perceiving the face c Reading the Brain Kamitani and Tong used relationship of voxel activity and orientation to create an orientation decoder determined which orientation the person was seeing it was accurate Naselaris created a brainreading device with two methods 1 Structural encoding based on the relationship between voxel activation and features of scene straight lines on the left of the scene and curved lines on the right side 2 Semantic encoding based on the relationship between voxel activation and the type of scene might indicate the subject is looking at an outdoor scene