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CHAPTER 6

CHAPTER 6. PERCEPTION. Selective Attention. Selective Attention: the focusing of conscious awareness on a particular stimulus. Selective Attention.

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CHAPTER 6

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  1. CHAPTER 6 PERCEPTION

  2. Selective Attention • Selective Attention:the focusing of conscious awareness on a particular stimulus

  3. Selective Attention • Cocktail-Party Effect:the ability to attend to one of several speech streams while ignoring others (just as one is able to attend to one conversation among others at a cocktail party). In cases such as cocktail parties, the mention of one’s name is processed even if it occurs in an unattended speech stream.

  4. Selective Attention • Inattentional blindness: failing to see visible objects when our attention is directed elsewhere • Change blindness http://www.youtube.com/watch?v=vBPG_OBgTWg • Change deafness • Choice blindness http://www.youtube.com/watch?v=2pK0BQ9CUHk&feature=fvst

  5. Perceptual Illusions • Visual Capture • The tendency for vision to dominate all other senses. • Example?

  6. Perceptual Organization • Gestalt: • In German “Gestalt” means whole or form. The Gestalt psychologists studied perception and emphasized the fact that we can not study perception by examining its individual parts because quite often the whole is different (or more) than the sum of its parts.

  7. Form Perception • Figure-Ground • Relating to the principle that perceptions have two parts; a figure that stand out in good contour (the main elements of a scene), and an indistinct homogeneous background

  8. Look at the plus sign in the middle, the pink/purple dots will disappear and be replaced by a green ring.

  9. The circles are not moving. If you look at one it remains stationary while the other circles are moving.

  10. Stare at the four black dots in the center of the image for 30 - 60 seconds. Then quickly close your eyes and look at something bright (like a lamp or a window with sunlight coming through it). You should see a white circle with an image inside it.

  11. An Old Woman or a Young Lady?

  12. Gestalt Rules of Grouping • Proximity: The closer objects are to one another, the more likely they are to be perceived as belonging together We perceive the picture figures below as one group of 2 circles, one single circle and another group of 2 circles. Can you come up with examples of proximity as it relates to real life?

  13. Gestalt Rules of Grouping • Similarity: Similar elements are perceived to be part of a group. • For instance, all the players wearing blue shirts are from the University of Michigan, all those wearing red are represent the University of Wisconsin X O X O X O X O X O X O X O X O We see two columns of Xs and two columns of Os not four rows of XOXO

  14. Gestalt Rules of Grouping • Continuity:Sensations that appear to create a continuous form are perceived as belonging together Once an object appears to move in a particular direction, your brain assumes that the movement continues unchanged. On some smaller highways, for example, you can easily miss your turn unless you really pay attention to the signs. We tend to assume that the highway continues in the direction we’ve been moving

  15. Gestalt Rules of Grouping • Connectedness • We perceive spots, lines, or areas as a single unit when uniform and linked

  16. Gestalt Rules of Grouping • Closure • The tendency to fill in missing contours to form a complete object We perceive these objects as a circle and a square. http://www.exploratorium.edu/brain_explorer/jumping.html

  17. Gestalt Rules of Grouping

  18. Gestalt Rules of Grouping • Common Fate:Sets of objects that move in the same direction at the same speed are perceived together • Examples: A flock of birds flying in a V formation, though separated in space, will be perceived as a group

  19. Depth Perception • Depth Perception:The perception of distance, allowing us to experience the world in three dimensions. • Monocular Depth cues • Binocular Depth cues

  20. Depth Perception • Visual Cliff Gibson and Walk discovered that 6 month old infants would not crawl to their mothers if the were on the “deep” side

  21. Depth Perception • Binocular Cues: Depth cues requiring the use of two eye

  22. Depth Perception • Retinal Disparity:A depth cue based on the difference between the retinal images received by each eye • Closer objects have more retinal disparity than objects farther

  23. Depth Perception • As retinal disparity increases, perceived distance _________________. • As retinal disparity decreases, perceived distance _________________.

  24. Depth Perception • Convergence:A depth cue resulting from rotation of the eyes so that the image of an object can be projected on each retina. The rotating of the eyes causes feelings of tension in the eye muscle. This tension is stronger when objects are closer

  25. Depth Perception • Monocular Depth cues:Depth cues requiring the use of only one eye • Linear Perspective • Relative Size • Reduced Clarity • Interposition/Overlapping • Texture Gradient • Relative Height

  26. Depth Perception • Relative Size:If two objects are assumed to be the same size, the object producing a larger image on the retina is perceived as closer than the one producing a smaller images

  27. Depth Perception • Interposition/Overlapping:Closer objects block the view of objects farther away

  28. Depth Perception • Reduced Clarity:Faraway objects seem less clear and less detailed

  29. Depth Perception • Texture Gradient:A graduated change in the texture, or “grain” of the visual field. Texture appears finer as distance increases and coarser as the distance decreases.

  30. Depth Perception • Relative height:More distant objects are usually higher in the visual field than those nearby

  31. Depth Perception • Linear Perspective:The closer together two converging lines are, the greater the perceived distance

  32. Depth Perception • Light and Shadow (Relative Brightness) A depth cue whereby dimmer objects appear to be farther away than bright objects

  33. Depth Perception • Relative Motion (Motion Parallax) When we are in motion, nearby objects will appear to move by rapidly while objects that are farther away will appear to move more slowly

  34. Motion Perception • Our basic assumption is that shrinking objects are retreating, not shrinking and that enlarging objects are approaching • Stroboscopic Motion:the illusion of movement produced by showing the rapid progression of images or objects that are not moving at all • Phi Phenomenon: An illusion of apparent movement when two lights flash on and off in quick succession. The light appears to move from one location to the other • http://www.youtube.com/watch?v=gAvTTlXyzmE&feature=related

  35. Perception • Perceptual Constancy: The ability to maintain a perception of the properties of an object (e.g. size, shape, color) regardless of changes in the actual stimulus conditions, such as the level of illumination, or image size on the retina

  36. Perceptual Interpretation • Our perception is due to an interaction between nature and nurture • Critical Period • The critical period for normal sensory and perceptual development is in infancy

  37. Perceptual Adaptation • Humans are able to adapt perceptually. When people wear displacement goggles, they manage to adapt their movements and, with practice, to move about with ease. (Although kittens and monkey can also adapt, chicks cannot)

  38. Perception • Perceptual Set A readiness or predisposition to perceive a stimulus in a certain way. Perceptual sets can save us time that is usually consumed by additional detail processing of stimulus features, but they can also lead to perceptual errors. Once we have formed a wrong idea about reality, we have more difficulty seeing the truth

  39. Rat-Man Illusion

  40. What do these letters spell? Folk Croak Soak Yolk

  41. Perception • Schemas: • Mental representation of what we know, and have come to expect about the world

  42. Perception • Context Effects • A given stimulus may trigger radically different perceptions because of the immediate context. For example, we discern whether a speaker said “morning” or “mourning” or “dye” or “die” from the surrounding words.

  43. Perception and the Human Factor • Human Factors Psychologists: Explore how people and machines interact and how physical environments can be adapted to human behaviors. They help to design appliances, machines, and work settings that fit our natural perceptions.

  44. Is There Extrasensory Perception? • Extrasensory Perception (ESP): alleged awareness of external events by other means than the known sensory channels. • Parapsychology: the systematic study of alleged psychological phenomena involving the transfer of information or energy that cannot be explained in terms of presently known scientific data or laws

  45. Is There Extrasensory Perception? • Three most testable varieties of ESP • Telepathy: mind reading, thought transference • Clairvoyance: the alleged ability to “see” beyond the normal range of sight, such as distant or hidden objects or events in the past or future • Precognition: the purported ability to see or experience future events

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