1. SENSATION AND PERCEPTION
UNIT IV
SENSATION AND PERCEPTION

2. Sensation
Sensation
a process by which our sensory receptors and nervous system receive and represent stimulus energy
(sensory stimuli > transduction to neural message > brain)
Perception
a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

3. Sensation
Our sensory and perceptual processes work together to help us sort out complex processes

4. Sensation All 4s will apply each term to a children’s story or movie…
Bottom-Up Processing
analysis that begins with the sense receptors and works up to the brain’s integration of sensory information
Top-Down Processing
information processing guided by higher-level mental processes
as when we construct perceptions drawing on our experience and expectations
All 4s will apply each term to a children’s story or movie…

5. 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
Using sensory details, imagine and describe how you experience the following stimuli:
Sunshine through your window at 5:45 a.m
Loud classical music during class
Sour Patch Kids while watching a movie
A large hammer in your hand

6. Sensation Thresholds Absolute Threshold Difference Threshold
minimum stimulation needed to detect a particular stimulus 50% of the time (Ex: passing car)
In partners or trios, come up with another example to explain to the class
Difference Threshold
minimum difference between two stimuli required for detection 50% of the time (Ex: flower color)
just noticeable difference (JND)

7. Sensation- 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 because:
detection depends partly on person’s:
Experience – Expectations -Motivation -Level of fatigue
Kellan leaves work at 10 am. After stopping at the bank, he pulls out onto the highway to head home. Right as he turns onto the highway, a car full of 6 men dressed in masks rush into the bank behind him. Using Signal Detection Theory, predict why he may or may not notice. Person #1- Create an explanation and Person #4 create an alternative. Be ready to share in 3 minutes.

8. Sensation- Thresholds25 50 75
100
Low
Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
Subliminal
When stimuli are below one’s absolute threshold for conscious awareness
(Advertisements…)

9. Sensation- Thresholds
Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage
light intensity- 8%
weight- 2%
tone frequency- 0.3%
*Using one category from above, create a real-world example
Sensory adaptation- diminished sensitivity as a consequence of constant stimulation
1. Hit your forearm. Stop and respond.
2. Continuously hit your forearm for 30 sec.
…Hot peppers?

10. Ernst Heinrich Weber (1795–1878) was one of the first people to approach the study of the human response to a physical stimulus in a quantitative fashion. His law states that the just-noticeable difference between two stimuli is proportional to the magnitude of the stimuli.
Gustav Theodor Fechner (1801–1887) later offered an elaborate theoretical interpretation of Weber's findings, in which he attempted to describe the relationship between the physical magnitudes of stimuli and the perceived intensity of the stimuli

11. Vision Transduction conversion of one form of energy to another
in sensation, transforming of stimulus energies into neural impulses
(sensory stimuli > transduction to neural message > brain)

12. Vision
Wavelength
the distance from the peak of one wave to the peak of the next (which distinguish color differences)
Hue
dimension of color determined by wavelength of light
Intensity
amount of energy in a wave determined by amplitude
brightness
loudness

13. Vision- Physical Properties of Waves
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)

14. The spectrum of electromagnetic energy

15. Vision

16. Vision http://youtu.be/cFVbLnXWn6A
Pupil- adjustable opening in the center of the eye
Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
Lens- transparent structure behind pupil that changes shape to focus images on the retina
Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information
Fovea- central point in the retina, around which the eye’s cones cluster

17. Vision

18. Vision
Accommodation- the process by which the eyes lens changes shape to help focus near or far objects on the retina

19. Vision Acuity- the sharpness of vision
Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina
Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

20. Retinas Reaction to Light- Receptors
Rods
peripheral retina
detect black, white and gray
twilight or low light
Cones
near center of retina
fine detail and color vision
daylight or well-lit conditions

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

23. Retina’s Reaction to Light
Optic nerve- nerve that carries neural impulses from the eye to the brain
Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there

24. Vision

25. Pathways from the Eyes to the Visual Cortex

26. Visual Information Processing
Feature Detectors
nerve cells in the brain that respond to specific features
shape
angle
movement
Stimulus
Cell’s
responses

27. Visual Information Processing
Parallel Processing
simultaneous processing of several aspects of a problem simultaneously

28. Visual Information Processing
Trichromatic (three color) Theory
Young and Helmholtz
three different retinal color receptors
red
green
Blue

29. Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design

30. Visual Information Processing
Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” red green green red blue yellow yellow blue black white white black

31. Opponent Process- Afterimage Effect

32. Visual Information Processing
Color Constancy
Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

33. Audition Audition http://youtu.be/PeTriGTENoc Frequency Pitch
the sense of hearing
Frequency
the number of complete wavelengths that pass a point in a given time
Pitch
a tone’s highness or lowness
depends on frequency

34. Vision- Physical Properties of Waves
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)

35. The Intensity of Some Common Sounds

37. Audition- The Ear http://youtu.be/ahCbGjasm_E Middle Ear Inner Ear
chamber between eardrum and cochlea containing three tiny bones (auditory ossicles- the smallest bones in the body) that concentrate the vibrations of the eardrum on the cochlea’s oval window
hammer/malleus
anvil/incus
stirrup/stapes
Inner Ear
innermost part of the ear, contining the cochlea, semicurcular canals, and vestibular sacs
Cochlea
coiled, bony, fluid-filled tube in the inner ear through which
EXPLAIN WHAT IS HAPPENING IN YOUR EAR AS YOU HEAR:

38. Audition
Place Theory
the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated
Frequency Theory
the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch
#1 and #4, say something to your partner in two different pitches. Partners- EXPLAIN WHY/HOW WE HEAR DIFFERENCES IN PITCH USING BOTH THEORIES. Which do you agree with and why?

39. Audition Conduction Hearing Loss
hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea
Nerve (Sensorineural) Hearing Loss
hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

40. Audition
Older people tend to hear low frequencies well but suffer hearing loss for high frequencies 1
time 10
times
100
1000 32 64
128
256
512
1024
2048
4096
8192
16384
Frequency of tone in waves per second
Low
Pitch
High
Amplitude required for
perception relative to
20-29 year-old group

41. Touch Skin Sensations pressure warmth cold pain
only skin sensation with identifiable receptors
warmth
cold
pain

42. Pain Gate-Control Theory http://youtu.be/vnChL9VSmeQ
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain

43. Taste Taste Sensations Sweet= Sour= Salty= Bitter= Umami=
Sensory Interaction
the principle that one sense may influence another
as when the smell of food influences its taste
Apply to real-life example involving other senses.

44. Smell: Receptor cells>Olfactory bulb>Olfactory Nerves to Temporal lobe and primary smell cortex>Limbic system w memory and emotions
Receptor cells in
olfactory membrane
Nasal
passage
Olfactory
bulb
nerve

45. Age, Sex and Sense of Smell
Women
Men
Age Group 4 3 2
Number
of correct
answers
Women and young adults
have best sense of smell

46. Body Position and Movement
Kinesthesis
the system for sensing the position and movement of individual body parts
Vestibular Sense
the sense of body movement and position
including the sense of balance