Sensation and Perception

1. SENSATION AND PERCEPTION

2. Sensation & Perception
• How Does Stimulation Become Sensation?
• How Are the Senses Alike? How Are They
Different?
• What Is the Relationship between Sensation
and Perception?

3. How Does Stimulation Become
Sensation?
• Transduction: Changing Stimulation to
Sensation
• Thresholds: The Boundaries of Sensation
Signal Detection Theory

4. Transduction
• Transforming signals into neural impulses.
• Information goes from the senses to the thalamus , then
to the various areas in the brain.

5. Sensory Adaptation
• Decreased
responsiveness to
stimuli due to constant
stimulation.
Do you feel your underwear all day?

6. Cocktail-party phenomenon
• The cocktail party effect
describes the ability to focus
one's listening attention on a
single talker among a mixture of
conversations and background
noises, ignoring other
conversations.
• Form of selective attention.

7. How Are the Senses Alike? How Are
They Different?
• Vision: How the Nervous System Processes Light
• Hearing: If a Tree Falls in the Forest . . . How the
Other Senses Are Like Vision and
• Hearing
Synesthesia: Sensations across the Senses
Energy Senses Chemical Senses

8. Energy v. Chemical senses
Energy Senses Chemical Senses

9. Vision

10. Step One: Gathering Light
The Eye
Light enters through
a narrow opening
Cornea – transparent eye
cover
Iris – muscle; colored
part of the eye
Pupil – opening in the iris
• Sensitive to light and
emotion

11. Step Two: Within the Eye

12. Step Three: Transduction

13. Step Four: In the Brain
• Feature
detectors-
– Hubel and Wiesel
– groups of
neurons in the
visual cortex
respond to
different types of
visual images.

14. Feature Detectors

15. Theories of
color vision:
Explain our
ability to
distinguish
between colors
Trichromatic
theory
•Young-Helmholtz:
three types of
receptors (cones)
all others
variations
Opponent-
process theory
•Hering: three
types of bipolar
receptors
•Supported by
negative
afterimages
Thought to
work together:
•Thricomatic:
Cones
•Opponent-
Process:
Thalamus
Color Vision

16. Trichromatic Theory
Three types of cones:
• Red
• Blue
• Green
• These three types of
cones can make millions
of combinations of
colors.
• Does not explain
afterimages or color
blindness well.

18. Opponent-Process theory
The sensory receptors
come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is
stimulated, the
other is inhibited.

19. Plates from a Test for Color Blindness

23. Principles of Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

24. Perceptual Organization
• Figure – Ground Perception
– Ambiguous, unstable figures, we shift back & forth

25. 1. Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

26. 1. Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

27. Gestalt Rules for Perceptual
Organization

28. Perception of Motion
• Visual perception of motion is based on change
of position relative to other objects
• Illusions of movement
– Stroboscopic motion (class discussion, how
do we know that a train moves?)
• Induced Motion:
http://psychlab1.hanover.edu/Classes/Sensati
on/induced/index.html

29. • Binocular Cues
– Retinal disparity
– Convergence
• Monocular cues
Depth Perception

30. Constancy
• Acquired through experience; creates stability
– Size Constancy
– Color Constancy
– Brightness Constancy
– Shape Constancy

32. Faces
• http://www.michaelbach.de/ot/fcs_hollow-
face/index.html

33. Lightness Perception
• http://persci.mit.edu/demos/gaz/main-
frameset.html

34. Turning Tables
• http://www.michaelbach.de/ot/sze_shepardT
ables/index.html

35. Perception and Culture

36. Hearing: Transduction in the Ear

37. Pitch Theories
• Different hairs vibrate
in the cochlea when
they different pitches.
• So some hairs vibrate
when they hear high
and other vibrate
when they hear low
pitches.
Place Theory
• The height of the
wave gives us the
amplitude of the
sound.
• The frequency of the
wave gives us the
pitch if the sound.
Frequency Theory

38. Deafness
• Conduction Deafness
– Something goes wrong with the sound and the vibration on the way
to the cochlea.
• Nerve (sensorineural) Deafness

39. Touch
• Cutaneous Senses:
Receptors located in our
skin.
• Dermatomes

40. • Gate control theory: sensations are mediated
by neural gates in the spinal cord that lalow
them to continue to brain
Pain

41. Taste
• We have bumps on our
tongue called papillae.
• Taste buds are located
on the papillae (they
are actually all over the
mouth).
• Sweet, salty, sour and
bitter.

42. • Primary olfactory cortex
• Orbitofrontal cortex
• Amygdala
Olfaction

43. BODY POSITION SENSES

44. Vestibular Sense
• Tells us where our body
is oriented in space.
• Our sense of balance.
• Located in our
semicircular canals in
our ears.

45. Kinesthetic Sense
• Tells us where our body
parts are.
• Receptors located in our
muscles and joints.

46. What Is the Relationship between
Sensation and Perception?
• Perceptual Processing: Finding Meaning in
Sensation
• Perceptual Ambiguity and Distortion
Theoretical Explanations for Perception Seeing
and Believing

47. Perception
• We see things
• How do our minds make our worlds?

48. Thresholds
Absolute threshold:
• The absolute threshold is
the smallest amount of
stimulus we can detect.
Difference threshold:
• How much does a
stimulus need to change
before we notice the
difference?

49. Weber’s Law

50. Stepping Feet
• http://www.michaelbach.de/ot/mot-
feetLin/index.html