1. Sensation and Perception Unit 4

2. Sensation and Perception
input about
the physical world
Perception
Interpretation and
organization of input
Conscious
experience

3. Sensation Input about physical world
How sensory receptors & nervous system receive stimulus energies from environment
Raw information

4. perception How we organize & interpret sensory information
Raw information is constructed into our experiences

5. Form Perception & Feature Analysis
Bottom-Up Processing
Based upon properties of the stimulus (e.g., patterns of light & dark areas
Process this way when we have no prior knowledge, start at bottom and work our way up
Top-Down Processing
Based upon higher-order information (e.g., prior knowledge & context)
Process this way when we have prior knowledge, start at top and work to process details

6. Bottom-up Processing
Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

7. THE CHT Top-Down Processing
Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations.
THE CHT

8. Top down processing
Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

10. Figure 4.26 Bottom-up versus top-down processing

11. The Forest has Eyes – Bev Doolittle
Bottom-up vs. top-down
The Forest has Eyes – Bev Doolittle

13. Selective Attention
We focus on a very limited aspect of what we experience and ignore the rest
Like a flashlight beam!

14. Cocktail Party Effect:
The ability to attend selectively to one voice among many UNTIL you hear your name or the name of someone close to you

15. Sensation and Perception Unit 4

16. Sensation and Perception
input about
the physical world
Perception
Interpretation and
organization of input
Conscious
experience

17. Sensation Input about physical world
How sensory receptors & nervous system receive stimulus energies from environment
Raw information

18. perception How we organize & interpret sensory information
Raw information is constructed into our experiences

19. Form Perception & Feature Analysis
Bottom-Up Processing
Based upon properties of the stimulus (e.g., patterns of light & dark areas
Process this way when we have no prior knowledge, start at bottom and work our way up
Top-Down Processing
Based upon higher-order information (e.g., prior knowledge & context)
Process this way when we have prior knowledge, start at top and work to process details

20. Bottom-up Processing
Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

21. THE CHT Top-Down Processing
Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations.
THE CHT

22. Top down processing
Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

24. Cocktail Party Effect:
The ability to attend selectively to one voice among many UNTIL you hear your name or the name of someone close to you

25. Selective Inattention
Inattentional blindness
Failing to see visible objects when our attention is directed elsewhere
We are “blind” to all but a tiny sliver of the immense array of visual stimuli constantly before us
Psychologists estimate our 5 senses take in 11,000,000 bits of information/second!
We CONCIOUSLY process about 40 bits
We UNCONCIOUSLY process remaining 10,999,960 bits
Change blindness (SIMONS-Gorilla!)
Failing to notice changes in the environment
Magicians exploit our change blindness by riveting our attention on one hand’s dramatic act with inattention to the change accomplished by the other hand
Watch Gorilla

26. How Do We Study Sensation?
Psychophysics
Study of the relationship b/t a physical stimulus and your perception of it.
Concerned mostly with physical attributes of the stimulus (e.g., amp & loudness).
OLDEST FORM OF PSYCH (sometimes asked on AP Test)- goes back to ancient Greeks
Now on to the Stimulus Question:
- October 22 Fechner’s Insight Day
Gustav Fechner
Father of Psychophysics
(and a lot of fun at parties)

27. Psychophysics
A study of the relationship between physical characteristics of stimuli and our psychological experience with them.
Physical World
Psychological World
Light
Brightness
Sound
Volume
Pressure
Weight
Sugar
Sweet

28. Thresholds
Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
Proportion of “Yes” Responses
Stimulus Intensity (lumens)
OBJECTIVE 2| Distinguish between absolute and difference thresholds, and discuss whether we can sense stimuli below our absolute thresholds and be influenced by them.

29. Selective Inattention
Inattentional blindness
Failing to see visible objects when our attention is directed elsewhere
We are “blind” to all but a tiny sliver of the immense array of visual stimuli constantly before us
Psychologists estimate our 5 senses take in 11,000,000 bits of information/second!
We CONCIOUSLY process about 40 bits
We UNCONCIOUSLY process remaining 10,999,960 bits
Change blindness (SIMONS-Gorilla!)
Failing to notice changes in the environment
Magicians exploit our change blindness by riveting our attention on one hand’s dramatic act with inattention to the change accomplished by the other hand
Watch Gorilla

30. How Do We Study Sensation?
Psychophysics
Study of the relationship b/t a physical stimulus and your perception of it.
Concerned mostly with physical attributes of the stimulus (e.g., amp & loudness).
OLDEST FORM OF PSYCH (sometimes asked on AP Test)- goes back to ancient Greeks
Now on to the Stimulus Question:
- October 22 Fechner’s Insight Day
Gustav Fechner
Father of Psychophysics
(and a lot of fun at parties)

31. Psychophysics
A study of the relationship between physical characteristics of stimuli and our psychological experience with them.
Physical World
Psychological World
Light
Brightness
Sound
Volume
Pressure
Weight
Sugar
Sweet

32. Thresholds
Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
Proportion of “Yes” Responses
Stimulus Intensity (lumens)
OBJECTIVE 2| Distinguish between absolute and difference thresholds, and discuss whether we can sense stimuli below our absolute thresholds and be influenced by them.

33. Detection Absolute Threshold Intensity No No No Yes Yes Detected
Observer’s Response
Detected
Tell when you (the observer) detect the light.

34. Sensation & Perception
Measuring Sensory Experience Absolute Sensory Thresholds
9/18/2018
Vision: A single candle flame from 30 miles on a dark, clear night
Hearing: The tick of a watch from 20 feet in total quiet
Smell: 1 drop of perfume in a 3-room apartment
Taste: 1 teaspoon sugar in 2 gallons of water
Touch: The wing of a bee on your cheek, dropped from 1 cm
From:
Davis, S., & Palladino, J. (1997). Discovering Psychology.
Upper Saddle River, NJ: Prentice Hall.
©2001 Prentice Hall

35. Signal Detection Theory (SDT)
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on:
Person’s experience
Expectations
Motivation
Level of fatigue

36. Subliminal Threshold
Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness.

37. Subliminal Stimulation (???)
Study More For
the next test!??
Can we process information
without being aware of it?

38. “Is this person happy or sad?” Most subjects will answer HAPPY!
SO WHAT?
Priming: the unconscious activation of certain associations which predisposes memories, thoughts or responses
Stopped here
“Is this person happy or sad?”
Most subjects will answer HAPPY!

39. Difference Threshold
Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND).
Difference
Threshold No No
Yes
Observer’s Response
Tell when you (observer) detect a difference in the light.

40. Difference Thresholds (JND)
What is the minimum
difference between two
stimuli that a person can
detect 50% of the time?

41. Difference Thresholds (JND)
Light - 8% difference
Weight - 2% difference
Sound - 0.3% difference
(Ernst) Weber’s Law
“Regardless of magnitude, two stimuli must
differ by a constant proportion for the
difference to be noticeable.”

42. Weber’s Law
Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = dI/I.
Stimulus
Constant (k)
Light 8%
Weight 2%
Tone
0.3%

43. Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Preview Question 3: What is the function of sensory adaptation?
Put a band aid on your arm and after awhile
you don’t sense it.

44. Touch (you will never forget the
Sensory Adaptation
The most important aspect of our environment is...
CHANGE
CHANGE
Our senses are designed to notice changes:
Visual
Auditory
Olfactory
Touch (you will never forget the
Underwear example…..)
CHANGE
CHANGE
CHANGE
CHANGE
CHANGE
CHANGE
CHANGE
Sensory Adaptation

45. Quick Conversation: Homecoming
Talking with Partner, take turns applying each of these to Homecoming Weekend!
Sensation
Perception
Difference Threshold/Weber’s Law
What the brain notices the most: ______
Sensory Adaptation
Priming
Signal Detection Theory
Change Blindness
Inattentional Blindness
Cocktail Party Effect

46. Vision

47. Transduction
In sensation, the transformation of stimulus energy into neural impulses. Phototransduction: Conversion of light energy into neural impulses that the brain can understand.
OBJECTIVE 4| Define transduction, and specify the form of energy our visual system converts into neural messages our brain can interpret.

48. The Stimulus Input: Light Energy
Visible
Spectrum
Both Photos: Thomas Eisner

49. Light Characteristics
Wavelength (hue/color)
Intensity (brightness)
Saturation (purity)

50. Wavelength (Hue)
Hue (color) is the dimension of color determined by the wavelength of the light. Wavelength is the distance from the peak of one wave to the peak of the next.

51. Different wavelengths of light result
Wavelength (Hue)
Violet
Indigo
Blue
Green
Yellow
Orange
Red
400 nm
700 nm
Short wavelengths
Long wavelengths
Different wavelengths of light result
in different colors.

52. Intensity (Brightness)
Intensity Amount of energy in a wave determined by the amplitude. It is related to perceived brightness.

53. Intensity (Brightness)
Blue color with varying levels of intensity.
As intensity increases or decreases, blue color
looks more “washed out” or “darkened.”

54. Purity (Saturation) Monochromatic light added to green and red
Saturated
Saturated
Monochromatic light added to green and red
makes them less saturated.

55. The Eye
OBJECTIVE 5| Describe the major structure of the eye, and explain how they guide the incoming ray of light toward the eye’s receptor cells.

56. Parts of the eye
Cornea: Transparent tissue where light enters the eye.
Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light.
Lens: Focuses the light rays on the retina.
Retina: Contains sensory receptors that process visual information and sends it to the brain.

57. The Lens
Lens: Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

58. The Lens
Nearsightedness: A condition in which nearby objects are seen more clearly than distant objects. Farsightedness: A condition in which faraway objects are seen more clearly than near objects.

60. Retina
Retina: The light-sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information.

62. How the Human Eye Sees cornea pupil lens iris lens retina retina rods
Light waves pass through the ______________( ), ____________ ( ) and )___________
( ).
The__________ (______________) controls the amount of light entering the eye by controlling the size of the pupil.
The ___________ changes shape (_______________) to focus the incoming light onto the ___________.
As the light strikes the _____________, the light energy activates the ________ and ________ (_______________), the central area where they ______and ________ cluster is the _________.
Signals from the_________ and _________ and collected by the ____________, which transmit the information to ____________. The ________________ axons are bundled together to form the ______________, which transmits information to the ______________ and then ___________in the brain.
The _____________ leaves the eye, creating a “___________” because no receptor cells are located there.
cornea
protects eye
pupil
lens
adjustable opening
transparent structure behind pupil
iris
colored muscle
lens
accommodates
retina
retina
rods
cones
photoreceptors
rods
cones
fovea
rods
cones
bipolar cells
ganglion cells
ganglion cells
optic nerve
thalamus
visual cortex
optic nerve
blind spot

63. Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the brain.
Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. This creates a blind spot.
Fovea: Central point in the retina around which the eye’s cones cluster.

64. Photoreceptors
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

65. Bipolar & Ganglion Cells
Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which converge to form the optic nerve.
**in terms of order, think PBG…like a PBJ 

67. Rods and Cones Cones Rods Color and detail Sensitive in dim light
First make you aware of an object’s presence
Black, white, and gray
Nocturnal animals have more rods

68. Visual Information Processing
Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.
**in terms of order, think OTV…alphabetical order
Preview Question 6: How does the brain process visual information?

70. Feature Detection
Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement.

71. Sensation & Perception
9/18/2018
Vision Hubel & Wiesel’s Experiment
Some cells in the visual cortex respond only to certain types of visual information, for example, a diagonal line moving up and down.
These cells are called feature detectors.
Figure 3.8 from:
Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.
Source:
Hubel, D. H.., & Wiesel, T.N. (196Davis 2). Receptive fields, binocular interaction and functional architecture in the cat’s visual cortex. Journal of Physiology, 160,
©2001 Prentice Hall

72. Shape Detection
Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses.

73. Perception in Brain
Our perceptions are a combination of sensory (bottom-up) and cognitive (top-down) processes.