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Cognitive Psychology, Fifth Edition, Robert J. Sternberg Chapter 3 Chapter 3: Visual Perception.

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Presentation on theme: "Cognitive Psychology, Fifth Edition, Robert J. Sternberg Chapter 3 Chapter 3: Visual Perception."— Presentation transcript:

1 Cognitive Psychology, Fifth Edition, Robert J. Sternberg Chapter 3 Chapter 3: Visual Perception

2 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Some Questions of Interest How can we perceive an object like a chair as having a stable form, given that the image of the chair on our retina changes as we look at it from different directions?

3 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Some Questions of Interest What are two fundamental approaches to explaining perception? What happens when people with normal visual sensations cannot perceive visual stimuli?

4 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perception Is… The process of recognizing, organizing, and interpreting information How do you recognize these items?

5 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Basic Concepts Distal object –Grandmas face Informational medium –Reflected light from Grandmas face Proximal stimulation –Photon absorption in the rod and cone cells of the retina Perceptual object –Grandmas face

6 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perceptual Basics Sensory adaptation –Occurs when sensory receptors change their sensitivity to the stimulus –Constant stimulation leads to lower sensitivity Our senses respond to change –Ganzfeld effect

7 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perceptual Illusions Sometimes we cannot perceive what does exist Sometimes we perceive things that do not exist

8 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perceptual Illusions Sometimes we perceive what cannot be there

9 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perceptual Illusions Some other illusions to explore: –http://www.michaelbach.de/ot/#historyhttp://www.michaelbach.de/ot/#history

10 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Our Visual System Light travels through the eye and focuses on the retina –Electromagnetic light energy is converted into neural electrochemical impulses

11 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Our Visual System Three main layers of neural tissue in retina –Ganglion cells –Amacrine cells, horizontal cells, bipolar cells –Photoreceptors Rods and cones

12 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Visual Pathways in the Brain What/where hypothesis –One path for identifying Temporal lobe lesions in monkeys –Can indicate where but not what –Another for spatially locating Parietal lobe lesions in monkeys –Can indicate what but not where

13 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Visual Pathways: Alternative What/how hypothesis –Where something is located in space –How do we reach for it?

14 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Theories of Perception Bottom-up theories –Parts are identified, put together, and then recognition occurs Top-down theories –People actively construct perceptions using information based on expectations

15 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Bottom-Up Processing Theories Direct perception Template theories Feature-matching theories Recognition-by-components theory

16 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gibsons Theory of Direct Perception The information in our sensory receptors is all we need to perceive anything –Do not need the aid of complex thought processes to explain perception

17 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gibsons Theory of Direct Perception Use texture gradients as cues for depth and distance –Allows us to perceive directly the relative proximity or distance of objects

18 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gibsons Theory of Direct Perception Mirror neurons start firing ms after a visual stimulus

19 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Template Theories Basics of template theories –Multiple templates are held in memory –To recognize the incoming stimuli, you compare to templates in memory until a match is found See stimuli Search memory for a match

20 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Template Theories Weakness of theory –Problem of imperfect matches –Cannot account for the flexibility of pattern recognition system See stimuli No perfect match in memory Search for match in memory

21 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Feature-Matching Theories Recognize objects on the basis of a small number of characteristics (features) –Detect specific elements and assemble them into more complex forms –Brain cells that respond to specific features such as lines and angles are referred to as feature detectors

22 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Pandemonium Model Four kinds of demons –Image demons –Feature demons –Cognitive demons –Decision demons

23 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Participants asked what they saw on the Global level Local level Results depended on whether letters are more widely spaced Participants were faster at identifying local features of the letters Navon (1977)

24 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Hubel & Wiesel (1979) –Simple cells detect bars or edges of particular orientation in particular location –Complex cells detect bars or edges of particular orientation, exact location abstracted –Hypercomplex cells detect particular colors (simple and complex cells), bars, or edges of particular length or moving in a particular direction Physiological Evidence for Features

25 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Biederman (1987) –Describes how 3D images are identified –Breaks objects down into geons –Objects are identified by geons, relationship between them Recognition-by-Components (RBC) Theory

26 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Evidence for Geons Biederman & Cooper (1991) –Used visual priming to demonstrate the existence of geons in a picture naming task –Subjects were shown a series of fragmented pictures and were asked to identify the objects BUT there are neurons sensitive to viewpoint-invariant properties

27 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Top-Down Processing (Constructive Approach) Perception is not automatic from raw stimuli Processing is needed to build perception Top-down processing occurs quickly and involves making inferences, guessing from experience, and basing one perception on another

28 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Context effects Evidence for Top-Down Processing

29 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Configural-Superiority Effect Objects presented in context are easier to recognize than objects presented alone Task: Spot the different stimuli, press button

30 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Configural-Superiority Effect Measure reaction time Target alone = 1884Composite = 749 Target spotted faster in a context! TargetComposite

31 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Which Approach Is Right? Top-down or bottom-up –Perhaps a bit of both

32 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Object Perception Viewer-centered representation –Object is stored in the perspective seen –Store multiple views of object as seen under various conditions –Viewpoint dependent process Object-centered representation –Object is stored in a way that best represents the object –Viewpoint invariant process

33 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Object Perception Evidence supports both How to reconcile? –Maybe both contribute to object recognition –Two ends of a continuum that contribute to object recognition –Burgund & Tarr researched this issue

34 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Landmark-Centered Orientation Information is coded by its relation to a well-known or prominent item Consider your college campus –What is a prominent item you use to orient yourself on campus?

35 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gestalts View of Perception Basic tenet –The whole is more than a sum of its parts Law of Prägnanz –Individuals organize their experience in as simple, concise, symmetrical, and complete manner as possible

36 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gestalts Principles of Visual Perception

37 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gestalts Principles of Visual Perception Figure-ground –Organize perceptions by distinguishing between a figure and a background Proximity –Elements tend to be grouped together according to their nearness Similarity –Items similar in some respect tend to be grouped together

38 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Gestalts Principles of Visual Perception Continuity –Based on smooth continuity, which is preferred to abrupt changes of direction Closure –Items are grouped together if they tend to complete a figure Symmetry –Prefer to perceive objects as mirror images C B A D

39 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Pattern Recognition Systems Feature analysis system –Recognize parts of objects –Assemble parts into wholes Configurational system –Recognize larger configurations

40 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Tanaka & Farah (1993) –Participants studied Faces and names Pictures of homes and home owners names –At test, given only a piece of face (e.g., nose), whole face, whole home, or a piece of the home (e.g., window) Asked to recall names Evidence for Separate Systems

41 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Tanaka & Farah (1993) Results People have more difficulty recognizing parts of faces than parts of houses

42 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Fusiform Gyrus in Temporal Lobe Implicated in pattern recognition Studies illustrate it is active in facial recognition However, also active if high expertise in any item (birds, cars) recognition –Expert individuation hypothesis

43 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Prosopagnosia –Inability to recognize faces after brain damage –Ability to recognize objects is intact Associative agnosia –Difficulty with recognizing objects –Can recognize faces Evidence for Separate Systems

44 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Perceptual Constancy Object remains the same even though our sensation of the object changes –Size constancyvs. shape constancy

45 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Depth Perception The ability to see the world in three dimensions and detect distance –Vision only has a two-dimensional view –We must interpret the information given to perceive depth –We take flat images and create a three- dimensional view –Optical illusions demonstrate that this interpretation does not always have to be correct

46 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Texture gradients –Grain of item Relative size –Bigger is closer Interposition –Closer are in front of other objects Monocular Depth Cues

47 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Monocular Depth Cues Linear perspective –Parallel lines converge in distance Aerial perspective –Images seem blurry farther away Motion parallax –Objects get smaller at decreasing speed in distance

48 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Binocular Depth Cues Binocular convergence –Eyes turn inward as object moves toward you; brain uses this information to judge distance Binocular disparity –Each eye views a slightly different angle of an object; brain uses this to create a 3D image

49 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Agnosias, Ataxias, & Cognition Demonstrate the modularity of cognition Help us to understand what brain locations are associated with different types of higher-level processing Provide us with a model of how normal processing must work

50 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Deficits in Perception Disruption of the what pathway –Agnosia Inability to recognize and identify objects or people, despite having knowledge of the characteristics of the objects or people Shows the specialization of our perceptual systems

51 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Deficits in Perception Disruption of the what pathway –Simultagnosic Normal visual fields, yet act blind Perceives only one stimulus at a time single word or object

52 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Disruption of the what pathway –Prosopagnosia Inability to recognize faces, including one's own Cannot recognize person from face Knows a face is a face Can recognize individuals from voice Can recognize objects Can discriminate whether two faces are same or different Deficits in Perception

53 Cognitive Psychology, Sixth Edition, Robert J. Sternberg Chapter 3 Deficits in Perception Disruption of the how pathway –Optic ataxia Cannot use vision to guide movement Unable to reach for items


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