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Perception

Perception. Top-down processing. What do you see?. Perception is different from sensation. Wundt-Jastrow illusion The oscillating window illusion The horizontal-vertical illusion The Muller-Lyer Illusion. The oblique effect. Brain pathways and perception.

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Perception

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  1. Perception Top-down processing

  2. What do you see?

  3. Perception is different from sensation • Wundt-Jastrow illusion • The oscillating window illusion • The horizontal-vertical illusion • The Muller-Lyer Illusion

  4. The oblique effect

  5. Brain pathways and perception • From the retina, axons of ganglion cells travel as the optic nerve to the lateral geniculate nucleus (LGN) of the thalamus • From LGN cells, axons travel to the primary visual cortex, in the occipital lobe • From the primary visual cortex, axons project to visual association cortex, in the parietal and inferior temporal lobes

  6. Other visual pathways • To the SCN (suprachiasmatic nucleus) of hypothalamus • To accessory optic nuclei of brainstem and to cerebellum: Synchronize eye and head movements • To pretectum to control pupil diameter • To superior colliculi of the tectum, for control of visual attention

  7. Information processing • At each level in the visual pathways, more complex information is drawn from the stream • Hubel and Wiesel’s method (1977): Microelectrodes • Receptive fields: On and Off

  8. The Hermann Grid

  9. Receptive fields • The piece in the visual field to which a given cell responds. • Receptive fields for rods and cones are simple and round. Off On

  10. on on on off on on off off off on off off Examples of receptive fields Center-surround Cells: -Ganglion cells, LGN cells (both M and P), and layer IV of striate cortex Center off-surround on Center on-surround off

  11. Receptive fields and gray dots

  12. on off Examples... Simple cortical cells: Line border responds best to -contrasting bars -single straight edges -at a particular angle off on

  13. Complex cortical cells • Merge inputs from simple cells to detect • Stimuli over a larger area of the visual field • An edge at a particular angle anywhere in the field (not “on-off”) • Movement, often directionally • About half are binocular • Half of the binocular cells show ocular dominance • Some are retinal disparity detectors

  14. Complex cell fields Note: - the larger receptive field - no subdivision on-off -orientation responsiveness -directional sensitivity

  15. Combines information from the primary visual cortex to produce Orientation, movement, and color Three dimension views Spatial location of objects Visual association cortex

  16. Primary visual cortex: Sensory (Scotomas) Visual association cortex: Perceptual Achromatopsia Loss of movement perception Balint’s syndrome: Location Visual agnosias Prosopagnosia Effects of damage

  17. Agnosias • Prosopagnosia • Actually, an inability to identify particular faces • Duplicated as an inability to recognize particular cows, doors, cars • Problem is in distinguishing among similar examples of complex visual stimuli • Damage is inferior temporal

  18. Other agnosias • Apperceptive visual agnosias • Prosopagnosia • Achromatopsia • Associative visual agnosias • Inability to name seen objects, although they can copy them and know the word (“anchor”) • May get the word through circumlocutions (the milking farmer)

  19. Selective attention Reversible figures The cocktail party effect Dichotic listening experiments Perceptual illusions Visual capture Processes of organization

  20. Principles of organization • Gestalt psychology • Form perception • Figure-ground • Grouping: Pragnanz • Closure and completion • Proximity • Similarity • Continuation and Common Fate • Connectedness

  21. Form perception: Figure-ground Notice the effects of continuous boundaries on the goodness of form perception of the vase figure.

  22. Closing borders

  23. An example of completion at Mt. Rushmore

  24. Subjective contours

  25. Other subjective contours

  26. Gestalt laws of perception Proximity Pragnanz

  27. More Gestalt principles C C C B C C C C C C B C C C B B B B B B B C C C B C C C C C C B C C C C C C B C C C C C C B C C C C C C B C C C Continuation Similarity

  28. More Gestalt Principles... Common Fate Connectedness

  29. What principles here?

  30. Form and pattern perception • Templates? • Prototypes • Humphrey’s monkeys • Interested in individual monkey pictures • Not interested in individual cows and pigs • Exposure increased interest in cows and pigs • Experience sharpens prototypes

  31. Distinctive features • Rule prototypes: Ulrich Neisser (1964) EWAFTMX SQPRDGB LKZFECKH OBCQJUG EXNWKAE SDBPNRQ AFLXZMW BPOSRGQ • The man who mistook his wife for a hat

  32. Perceiving distinctive features • Context cues • Biederman’s (1990) geons • Cusps and joints

  33. Principles of organization • Depth perception • Monocular cues • Binocular cues • Examples: Fingerpointing, hole in hand • Motion perception • Size and position • Stroboscopic movement • Phi phenomenon

  34. The phi phenomenon

  35. Monocular Depth cues: Height, Interposition, and Relative Size

  36. What cues are here?

  37. Charles Sheeler, Classic Landscape, National Gallery, Feb. 26, 2000

  38. Perception phenomena • Perceptual constancy • Size and shape: The swelling hand • Brightness: Overhead • Perception as interpretation • The grasping visual illusion

  39. Ebbinghaus figures and the grasping illusion Franz, Gegenfurter, Bulthoff, & Fahle, 2000

  40. Perceptual Constancy and the Moon Illusion

  41. Expectations affect perceptions • Perceptual set • Expectations or schemas: Numbers and names • Context: TIME FLIES I CANT THEYRE TOO FAST CHO PHO USE CHOPHOUSE

  42. More context effects FOLK CROAK SOAK THE WHITE OF AN EGG

  43. LULB CALEM NUKKS SEUMO BAZER NORC NOONI MATOOT PREPPE TEBE Cognitive set EAP

  44. Social transmission of narrative • Three men, masked and armed with pistols, robbed the Glenwood State Bank yesterday morning at 9:30 a.m. They escaped in a Ford two-door bearing a 1971 Connecticut license plate, taking $647 in coins and $2,190 in five-dollar bills. A lieutenant in the Marines claims he saw the car going north at noon yesterday.

  45. Backmasking • Queen, Another one bites the dust • Queen, backwards • Psalm 23, backwards • Excerpt: Jabberwocky, Lewis Carroll • More Jabberwocky

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