Chapter 8

1. Chapter 8 Perception

2. Perception • Bottom-Up Process • An analysis of the action of feature detectors in a sensory experience • Top-Down Process • An analysis of the effects of expectations and prior learning on a sensory experience

3. Receptive Fieldsand Feature Detectors • Receptive Field • The portion of the visual field to which a cell in the nervous system responds when visually stimulated • Feature Detector • A visual neuron that is sensitive to a particular visual feature

4. + - Ganglion Cell Receptive Fields • On-center cells • Ganglion cells that respond in an excited fashion when light falls in the center and darkness falls on the outside Equal Lighting Center Off Center On

5. - - + + Ganglion Cell Receptive Fields • Off-center cells • Ganglion cells that respond in an excited fashion when light falls in the surround and darkness falls on the center

6. Cortical Feature Detectors • Simple Cells • Neurons in the striate cortex that respond to lines of a particular orientation in their receptive field

7. Depth Perception • The perception of depth arises from a combination of cues that creates the illusion of three dimensions • Binocular Cues to Depth • require both eyes • Monocular Cues to Depth • require only one eye

8. Binocular Cue ofRetinal Disparity • Each eye has a slightly different view of the world • The difference in views produces an impression of depth

9. Binocular Cue ofConvergence • A cue to depth resulting from the eyes turning inward to see near objects

10. Monocular Cues to Depth • Interposition

11. Monocular Cues to Depth • Relative Size

12. Monocular Cues to Depth • Linear Perspective

13. Monocular Cues to Depth • Relative Clarity

14. Monocular Cues to Depth • Texture Gradient

15. Monocular Cues to Depth • Relative Motion

16. Perceptual Constancies • The perceptual world appears constant even though the retinal image is constantly changing

17. Perceptual Constancies • Size Constancy • The tendency to see a figure as being the same size, despite changes in its retinal size • Shape Constancy • The tendency to see a form as unchanging, despite changes in its retinal size • Lightness Constancy • The tendency to see an object as being the same, even under different light intensities

18. Brightness Contrast

19. Ponzo Illusion • May be due to perspective cues

20. Mueller-Lyer Illusion

21. Ambiguous Figures

22. Conscious & Unconscious Processes in Perception • Blindsight: The case of D.B. • Vision loss in left visual field, resulting from brain surgery (hemianopia) • Shown stick in blind field - claims he cannot see it • But, he can accurately determine its orientation

23. Hemianopia

24. The Striate Cortex and Consciousness • Patients with damage to striate cortex (primary visual cortex in the Occipital Lobe) can respond to visual stimuli, even though they are unaware of them

25. Unconscious Processing in Sighted Subjects • Subjects presented with moving dots • One quadrant moving in a different direction • Although subjects claim they cannot tell which quadrant is different, they are very accurate

26. Parallel Processing of Visual Information • Many different brain areas process visual information simultaneously • Processing of form, depth, motion and color is done by different brain areas

27. Parallel Processing of Visual Information

28. Evidence for Parallel Processing:Damage to Extrastriate Cortex • Cortical Color Blindness • Due to damage to brain area that processes color • Cortical Motion Blindness • Due to damage to brain area that processes motion

29. Temporal Lobe Damage • Visual Agnosia • A visual disability that is characterized by seeing without knowing the meaning of what is seen. • The case of Dr. P - The Man Who Mistook His Wife for a Hat. • Disconnection syndrome: visual processing occurring, but meaning has been lost • Prosopagnosia • loss of ability to recognize faces resulting from brain damage

30. Red Green Blue Pink Green Red Purple Blue Black Pink Pink Purple The Stroop Effect People find this condition the hardest

31. Gestalt Psychology • Perception is not putting together parts, but seeing the whole • The whole is greater than the sum of its parts - Max Wertheimer

32. Gestalt: Apparent Movement • The Phi Phenomenon

33. Principles of Perceptual Organization • We group together elements in a consistent manner • Grouping by Proximity and Similarity

34. Principles of Perceptual Organization • The Principle of Continuity People tend to report seeing two continuous lines

35. Principles of Perceptual Organization • The Principle of Common Movement

36. Principles of Perceptual Organization • The Principle of Pragnanz (Good Figure)

37. Principles of Perceptual Organization • Figure-Ground Relationships

38. Perception of Meaningful Sounds • Language as a meaningful signal may have developed after the development of music • Language and music are controlled by separate brain areas.

39. Perception of Odors and Tastes • Conscious vs. Unconscious processing of smells • Smell influence the onset of women’s menstrual cycle • Women living together in a dorm eventually developed a common cycle • Same results occur when women smell androstenone extracted from axillary areas of other women • Women who sleep with men have a more regular menstrual cycle

40. Smells and Sexual Attraction • Major Histocompatibility Complex • Section of DNA that is similar in closely related individuals • People with similar MHC genetic profiles have similar smells • Women prefer the smell of men who do not have a similar MHC genetic profile to themselves

41. The Perception of Touch • Contact Comfort • Harry Harlow: Baby monkeys will seek out soft, warm surrogate mothers, even if they do not provide food