Perception 3

• What are the two approaches to perceptual organization discussed?

  The structuralist and gestalt approaches

  
• Why is it challenging to design a perceiving machine?

  Because visual input gives us ambiguous information about the 3D structure of the world
• What complicates the organization of visual scenes for computers?

  Image complexity makes it trickier for computers to organize the visual scene into distinct objects
• What is the main question addressed regarding depth perception?

  How do we perceive depth?
• What do humans use to infer depth in a visual cue?

  Many sources of information
• What are monocular cues?

  Cues that work with one eye
• What does the relative height cue indicate?

  Distant objects are seen as being smaller and higher in relation to closer items
• How are objects below the horizon perceived in terms of distance?

  They are seen as being more distant if their bases are higher
• What does the relative size cue indicate?

  If two or more objects are equal in physical size, the more distant one takes up less of your field of view
• What is necessary for judging distance using relative size?

  Previous knowledge about the relative sizes of objects
• What does the occlusion cue indicate?

  Closer objects will occlude the further away ones
• What does linear perspective refer to?

  Parallel lines extending away from the observer converge in the distance
• What does texture gradient indicate?

  Texture elements become smaller and more dense with distance
• What happens during foreshortening?

  Circles become ovals when the surface is tilted away
• What does motion parallax refer to?

  More distant objects glide past us more slowly than nearer objects as we move
• How do shadows contribute to depth perception?

  Cast shadows can create a strong perception of depth
• How does shading affect depth perception?

  The brightness of a surface depends on its orientation with respect to the light source
• What are binocular cues?

  Cues that require both eyes
• What does disparity in binocular cues refer to?

  It creates a difference in image location of an object seen by the left and right eyes
• What does the size of the disparity depend on?

  It depends on an object’s depth
• What is stereoscopic vision?

  Our two eyes receive a slightly different image of the world
• What is the horopter?

  A set of points in space which project to corresponding positions in the two retinas
• What does the horopter include?

  The fixation point where participants are supposed to look at the screen
• What happens to objects closer than the horopter?

  They have crossed disparities

  
• What happens to objects further than the horopter?

  They have uncrossed disparities

  
• How is depth information extracted from binocular disparities?

  Through the process of stereopsis
• What does the perception of depth rely on?

  A mix of bottom-up and top-down processes
• How is depth information also extracted?

  From binocular disparities via a process known as stereopsis
• What is the main question addressed in Part 2?

  How do we perceive objects?
• Who pioneered the structuralism approach?

  Wilhelm Wundt
• What did structuralism propose about perceptions?

  Perceptions are simply the sum of ‘atoms’ of sensation
• What was the Gestalt school a reaction against?

  Structuralism
• According to structuralist theorists, how are perceptual objects formed?

  By grouping a number of primary sensations

  
• What is the main argument of Gestalt psychologists?

  The whole form/configuration is greater than the sum of its parts
• How do Gestalt psychologists view objects?

  As stable, organized wholes
• What are illusory contours?

  Images that cause the perception of edges where there’s no change in luminance/color
• Why are illusory contours hard to explain through the structuralist approach?

  Because they do not fit the idea of perceptions being the sum of sensations
• What do Gestalt psychologists propose regarding perceptual organization?

  They propose principles by which elements in an image are grouped to create larger objects

  
• What is the law of Pragnanz?

  Of several geometrically possible organizations, the one that possesses the best, simplest, and most stable shape will occur