1. Sensation and Perception True or False??? 1. On a clear, dark night most of us can see a candle flame 30 miles away. 2. Advertisers are able to shape our buying habits through subliminal messages. 3. Constant eye movements prevent our vision from being seriously disrupted.

2. Introducing,….Sensation! “Seeing is believing.”  For each of the following visuals, simply write down what you see. (Do not share with your neighbor.)

6. Analyzing what we see…. Each visual provides sensory information that gives rise to two totally different perceptual interpretations. Each visual provides sensory information that gives rise to two totally different perceptual interpretations. Now, lets try it again… Now, lets try it again… Write down what you see first in the next visual image. Write down what you see first in the next visual image.

8. Sensation and visual images  Why is it that no matter how many times we look at the image, we tend to see the image we saw the first time we observed it?  First impression = schema  Have to consciously seek the other figure  After practice, we can see both images, but not simultaneously

9. So, what is Sensation & Perception?  Sensation  The physical energy we detect (with our senses) from the environment and encode as neural impulses (what we sense and send to the brain)  Perception  How we select, interpret and organize our sensations (how the brain interprets it)

10. In other words… Sensation provides the raw information that perception translates into our experiences Sensation provides the raw information that perception translates into our experiences

11. Sensation : The Forest Has Eyes  sensation and perception work together to sort out complex processes

12. Sensation and Perception (Work together)  Bottom-Up Processing (Sensation)  Sense receptors detect stimuli and send to the brain  the brain then integrates sensory information  Top-Down Processing (Perception)  information processing guided by higher-level mental processes  How we interpret sensations based on expectations and previous experiences

13. Top Down Processing Aoccdrnig to rscheearch at Cmabridge Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a word are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can still raed it wouthit a porbelm. This is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the word as a wlohe.

14. Top Down Processing How were you able to immediately make sense of these scrambled words? How were you able to immediately make sense of these scrambled words? Our experience and expectations enable us to immediately perceive the scrambled letters as meaningful words and sentences. Our experience and expectations enable us to immediately perceive the scrambled letters as meaningful words and sentences. IOW: Higher level processes guide our perceptions. IOW: Higher level processes guide our perceptions.

15. Distinguishing Between Sensation and Perception See Handout See Handout 1. “Blotch”: (5.2) 2. Fraser Spiral (5.2) a.Place one finger on any line composing the spiral. b.Place a finger from your other hand beside it and begin tracing the circle while holding your first finger in place. c.What happens?

16. Failures of Perception Prosopagnosia: complete sensation but incomplete perception (“face blindness”) Prosopagnosia: complete sensation but incomplete perception (“face blindness”) –Can sense visual information, but can’t recognize it (can’t relate stored knowledge to sensory input) –Damage to temporal lobe area (recognition)

17. Sensation- Basic Principles  Psychophysics  study of how physical energy relates to our psychological experience (Or: study of interaction between sensations we receive and our experience of them.)  Light- brightness  Sound- volume  Pressure- weight  Taste- sweetness

18. Gustav Fechner Pioneer in Psychophysics 1801-1887 (U. of Leipzig) 1801-1887 (U. of Leipzig) Theory: consciousness and matter coexist Theory: consciousness and matter coexist Mind / body: two aspects of fundamental unity Mind / body: two aspects of fundamental unity Stared at sun! Afterimage of blue and yellow Stared at sun! Afterimage of blue and yellow Mathematical relationship b/n force of stimuli and intensity of sensation Mathematical relationship b/n force of stimuli and intensity of sensation

19. Sensation- Thresholds  Absolute Threshold  minimum amount of stimulus one can detect 50% of the time  Difference Threshold  minimum difference between two stimuli required for detection 50% of the time (the smallest change in stimulus needed to detect that change)  AKA- just noticeable difference (JND)

20. Absolute threshold “An absolute threshold is not absolute…” “An absolute threshold is not absolute…”  What factors might affect the absolute threshold?  Repetition  Fatigue  Competing stimuli  Expectation

21. Sensation- Thresholds  Weber’s Law- percentage or ratio of difference between objects remains constant for JND, even when weight or dimensions change  light intensity- 8%  weight- 2%  tone frequency- 0.3%

22. Weber’s Law As a salesman, how might one use Weber’s law to increase chances of selling the following to one customer? As a salesman, how might one use Weber’s law to increase chances of selling the following to one customer? A. Built in ipod accessory: $100 B. New Truck: $25,000 C. Navigation system: $200 D. Sliding rear window: $125

23. Sensation- Thresholds  Signal Detection Theory  predicts how and when we detect the presence of a stimulus (signal) amid competing stimuli (noise, objects etc.)  assumes that there is no single absolute threshold  Factors influencing detection (response criteria)  experience  expectations  motivation  level of fatigue

24. Vision: Sensory Adaptation Sensory adaptation- diminished sensitivity to stimulus as a consequence of constant exposure Sensory adaptation- diminished sensitivity to stimulus as a consequence of constant exposure Eyes: constant quiver to ensure enough continual stimulation to eye’s receptors Eyes: constant quiver to ensure enough continual stimulation to eye’s receptors Otherwise full visual image is lost Otherwise full visual image is lost

25. Vision- Stabilized Images on the Retina

26. Sensation- Thresholds  Subliminal  When stimuli are below one’s absolute threshold for conscious awareness 0 25 50 75 100 Low Absolute threshold Medium Intensity of stimulus Percentage of correct detections Subliminal stimuli

27. 1957 James Vicary James Vicary 1/3000 second 1/3000 second Repetition Repetition Sales increase Sales increase –Popcorn= 57% –Coke = 18% –6 week study –Falsified results –Gateway to subliminal marketing, then images,“sexploitation”

29. “Priming Effect” Feel what we do not know and cannot describe (shapes our perceptions a tiny bit without our awareness) Feel what we do not know and cannot describe (shapes our perceptions a tiny bit without our awareness) subliminal images: Imperceptibly brief stimulus subliminal images: Imperceptibly brief stimulus

30. What’s the reasoning…? The average American will see over 6 million ads in a lifetime… The average American will see over 6 million ads in a lifetime… Appeal to the subconscious will make consumer feel more positively about a product Appeal to the subconscious will make consumer feel more positively about a product

31. Envelopes, Quarters and boxes…. (Meyers, p. 7) Can you detect a difference in weight between the two envelopes? Can you detect a difference in weight between the two envelopes? Can you detect a difference in weight between the two envelopes now? Can you detect a difference in weight between the two envelopes now? How can we explain this development? How can we explain this development?

32. Vision  How do we transform particles of light into meaningful images?  Transduction  conversion of one form of energy to another  in sensation, our sensory systems transform stimulus energies into neural impulses

33. Vision  Two physical characteristics of light help determine how we visually sense them… 1. Wavelength  the distance from the peak of one wave to the peak of the next (determines hue)  Hue: color we see determined by wavelength of light 2. Intensity  amount of energy in a light wave determined by amplitude  brightness  or loudness

34. Wavelengths and Color From shortest to longest… From shortest to longest…  Violet  Indigo  Blue  Green  Orange  Red (We turn our eye towards an object and the reflected light coming from the object enters our eye.)

35. Vision- Physical Properties of Waves (from an atom to a mile…) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Great amplitude (bright colors, loud sounds) Small amplitude (dull colors, soft sounds)

36. The spectrum of electromagnetic energy: (light that we transduce into color)

37. Vision

38. Match the following 1. Cornea D 2. Pupil A 3. Iris B 4. Lens C 5. Retina E a. Adjustable opening in the center of the eye b. Ring of muscle, color portion of the eye around pupil- controls size of pupil opening c. Transparent- behind pupil, changes shape to focus images on retina d. Protects eye, bends light to provide focus e. Eyes light sensitive inner surface- rods, cones, neurons that process visual info.

39. Vision  Accommodation- the lens changes shape to help focus near or far objects on the retina  Retina- the light-sensitive inner surface of the eye, containing receptor rods, cones and layers of neurons that begin the processing of visual information (transduction)

40. Retina’s Reaction to Light- Receptors  Rods (120 million!)  peripheral retina / peripheral vision  detect black, white and gray  twilight or low light  Cones (6 million)  near center of retina (Fovea)  fine detail and color vision  daylight or well-lit conditions

41. Rods and Cones

42. Making sense of our vision… So why is our peripheral vision more blurred than our focused vision? (in front of us) So why is our peripheral vision more blurred than our focused vision? (in front of us)  Cones = center of retina (fovea: hotline to visual cortex = fine detail)  Rods = periphery of retina How do you walk effectively on a trail on a very dark night? Why? How do you walk effectively on a trail on a very dark night? Why? Why can a cat see better than us at night? Why can a cat see better than us at night?

43. Vision- Receptors Receptors in the Human Eye ConesRods Number Location in retina Sensitivity in dim light Color sensitive?Yes Low Center 6 million No High Periphery 120 million

44. From the eye to the brain… Optic Nerve Rope-like axons form ganglion cells- carries information from the eye to the brain (1,000,000 messages at once!) Rope-like axons form ganglion cells- carries information from the eye to the brain (1,000,000 messages at once!)

45. Close your left eye- move forward to a spot in which the car disappears. What is this called? How do we explain it?

46. Retina’s Reaction to Light  Blind Spot- point at which the optic nerve leaves the eye- creates “blind spot” because no receptor cells located there  Fovea- central point in the retina, around which the eye’s cones cluster (contains only cones- direct connection to visual cortex through bipolar cells = fine detail)

47. Vision  Acuity- the sharpness of vision  Nearsightedness- nearby objects are more clear than distant objects because distant objects in front of retina  Farsightedness- faraway objects are more clear than near objects because the image of near objects is focused behind retina

48. Vision  Normal Nearsighted Farsighted Vision Vision Vision

50. Pathways from the Eyes to the Visual Cortex

51. Visual Information Processing Retina: Brain tissue / analyzes, encodes info & routes to Thalamus Retina: Brain tissue / analyzes, encodes info & routes to Thalamus Process becomes more complex as continues Process becomes more complex as continues

52. Visual Information Processing  Feature Detectors (Hubel and Wiesel, 1979)  Specific parts of the visual cortex respond to specific features (routed by Thalamus)  shape  angle  movement Stimulus Cell’s responses

53. Parallel Processing  feature detection is integrated in visual cortex in split second  IOW: angle, shape motion, depth etc of object are all processed in different parts of cortex and then instantly combined to create whole visual image)

54. Parallel Processing

55. Facial recognition = 30% of cortex Facial recognition = 30% of cortex Neural networks: synchronized integration Neural networks: synchronized integration –¼ of second- neurons, parts of brain collaborate at once(40 impulses per second) = conscious recognition!

56. How does this explain Prosopagnosia?

57. The Key to Perception Perception = combining sensory input with assumptions, expectations Perception = combining sensory input with assumptions, expectations

58. How the Brain Perceives Stare at the Necker Cube. What happens?

59. How can we explain our changing perception of the Necker Cube? Same image continues to meet your retina, your brain constructs varying perceptions every couple of seconds. Same image continues to meet your retina, your brain constructs varying perceptions every couple of seconds.

60. Illusory Contours Stare at the center of the image

61. Color Vision “Light rays are not colored. Color, like all aspects of vision, resides not in the object but in the theater of our brains.” “Light rays are not colored. Color, like all aspects of vision, resides not in the object but in the theater of our brains.”  Isaac Newton, 1704

62. How’s Your Color Vision?? http://www.neitzvision.com/ http://www.neitzvision.com/

63. Visual Information Processing  Trichromatic (three color) Theory  AKA: Young and Helmholtz theory  three different retinal color receptors (cones)  red  green  Blue  Combination of these cones = all colors of visible spectrum  Can not explain monochromatic / dichromatic color deficiency

64. Color-Deficient Vision  Dichromatic  Monochromatic

65. Opponent-Process Theory- opposing retinal processes enable color vision (in retina & thalamus, some neurons turned on/off by certain colors) “ON”“OFF” red green green red blue yellow yellow blue black white white black

67. Opponent-Process Theory Helps explain monochromatic and dichromatic color deficiency (and afterimage) Helps explain monochromatic and dichromatic color deficiency (and afterimage) Most theorize that we use a combination of both major theories (need both to explain color vision fully) Most theorize that we use a combination of both major theories (need both to explain color vision fully)

68. Visual Information Processing  Color Constancy  Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object (perception of color comes from object and those things around it)

69. Visual Disabilities Stroke, illness, surgery etc. can damage the visual cortex thus… Stroke victim case studies who have lost sense of visual movement Stroke victim case studies who have lost sense of visual movement Blindsight: sensation of vision is functional, but no perceptual awareness Blindsight: sensation of vision is functional, but no perceptual awareness Thus theory of 2 visual systems in brain: Thus theory of 2 visual systems in brain:  One for conscious perceptions  A second that guides our actions