Module 11

1

• Module 11
• Introduction to Sensation and Perception

2
Sensation

• Sensation
• the process by which our sensory receptors and
  nervous system receive and represent stimulus
  energy
• Perception
• the process of organizing and interpreting
  sensory information, enabling us to recognize
  meaningful objects and events

3
Sensation

• Sensation
• how do we change energy into sense
• Perception
• what do we do with our sensory information

4
Sensation

• Our sensory and perceptual processes work
  together to help us sort out complex images

5
Sensation

• Bottom-Up Processing
• analysis that begins with the sense receptors and
  works up to the brains integration of sensory
  information (piecing lines together to recognize
  the number 4)
• Top-Down Processing
• information processing guided by higher-level
  mental processes
• as when we construct perceptions drawing on our
  experience and expectations (think you know
  someone and as they get closer, realize that you
  dont)

6
Sensation- Basic Principles

• Psychophysics
• study of the relationship between physical
  characteristics of stimuli and our psychological
  experience of them
• Light- brightness
• Sound- volume
• Pressure- weight
• Taste- sweetness

7
Sensation- Thresholds

• Absolute Threshold
• minimum stimulation needed to detect a particular
  stimulus 50 of the time
• isnt constant can change with motivation and
  alertness
• Difference Threshold
• minimum difference between two stimuli required
  for detection 50 of the time
• just noticeable difference (JND)

8
Sensation- A. Thresholds

• Signal Detection Theory
• predicts how and when we detect the presence of a
  faint stimulus (signal) amid background
  stimulation (noise)
• assumes that there is no single absolute
  threshold
• detection depends partly on persons
• experience
• expectations
• motivation
• level of fatigue

9
Sensation- A. Thresholds

• Signal Detection Theory
• detection of stimuli involves decision processes
  as well as sensory processes
• Example riddle, shower/telephone

10

• Youre driving a bus with 12 passengers. At
  your first stop, 6 passengers get off. At the
  second stop, 3 get off. At the third stop, 2
  more get off, but 3 new people get on. What
  color are the drivers eyes?
• Did you detect the signal who is the driver?
  over the noise number of passengers?

11
Sensation- A. Thresholds

• Subliminal
• when stimuli are below ones absolute threshold
  for conscious awareness

12
Sensation- A. Thresholds

• Subliminal Messages
• Reverse Speech - Voices From The Unconscious

13
Sensation- Thresholds

• Difference Threshold
• minimum difference between two stimuli required
  for detection 50 of the time
• just noticeable difference (JND) we experience
  the difference threshold as a JND.

14

• Read the passage at the right.
• How many lines do you require to experience a
  noticeable difference?

15
Sensation- D. Thresholds

• Webers Law
• to be perceived as different, two stimuli must
  differ by a constant minimum percentage (rather
  than a constant amount)
• light intensity- 8 (1/60)
• weight- 2 (1/50)
• tone frequency- 0.3 (1/333)

16
Sensation- D. Thresholds

• Sensory Adaptation
• diminished sensitivity as a consequence of
  constant stimulation
• (wearing a new wristwatch)
• Selective Attention
• focusing of conscious awareness on a particular
  stimulus
• as in the cocktail party effect (listen to one
  voice, among many)

17
Now you see it, now you dont!
18
Perception

• Selective Attention
• Do you see circles with white lines or a cube?
• Because attention is selective, you only see one
  interpretation at a time.

19
Change Blindness

• Change Blindness is an example of Selective
  Attention
• Lab Demos

20
Change Blindness