Transcript Sensation_and_Perception

9/24

What do you see in the
first image?

What do you see in the
2nd image?
9/25


How does sensation and perception relate to this photo?
We will be watching a Psychology 101 video relating sensation &
perception to sports. Write down her brief explanation of why
people can interpret plays differently.
9/26
Have homework out (Auditory half sheet)
 Think about….
If you had to lose a major sense (vision,
hearing, taste, touch, smell), what would it be
and why?

© 2008 The McGraw-Hill Companies, Inc.
9/27
1.
A)
B)
C)
D)
Frequency is to pitch as ___________ is to ___________.
Wavelength; loudness
Amplitude; loudness
Wavelength; intensity
Amplitude; intensity
2. A decrease in sensory responsiveness accompanying an unchanging
stimulus is called:
A)
Sensory fatigue
B)
Accommodation
C)
Sensory Adaptation
D)
Sensory Interaction
© 2008 The McGraw-Hill Companies, Inc.
Sensation and Perception
Consciousness
Windows on the World

How we understand our
world

Two basic processes:


Sensation: Gathering
information
Perception: Interpreting
information
Basic Principles

Sensation


Transduction


The process of receiving stimulus energies
from the external environment
The process of transforming physical energy
into electrochemical energy (action potential)
Perception

The process of organizing and interpreting
sensory information
Sensation and Perception



Can you identify
anything meaningful
in these patterned
shapes?
Sensation is detecting
the different shapes
However, organizing
it into something is the
process of perception.
Perceptual Processing

Bottom-up Processing

Processing of sensory info as it enters the receptors and travels to
the brain




Face-value interpretation
Initiated by sensory input
Sensation  Perception
Top-Down Processing



Uses existing information (learning history) to interpret sensory
information
Initiated by cognitive processing
Perception  Sensation
Sensation and Perception

Look at the three boxes below. Write down
what color you think each box represents.
Sensation and Perception

The boxes are colored in lime, turquoise and rose.

If each student is receiving the same sensation of color
from each of the boxes, then why do some students have
different perceptions of the colors?
Sensation

Sensory Receptors

Specialized cells that detect and transmit
sensory information to the brain

These cells respond selectively to stimulation

Cells send signals via distinct neural pathways
Sensation (senses)

Photoreception (Vision)


Mechanoreception (Touch and Hearing)


Detection of light
Detection of pressure, vibration, and movement
Chemoreception (Smell and Taste)
Detection of chemical stimuli
Psychophysics: The study of how this physical
energy relates to our psychological experience.

Nature’s sensory gifts suit
each recipient’s needs….



A frog has eyes with receptor cells that only fire in
response to small, dark, moving objects.
A male silkworm moth has receptors so sensitive
to the female odor that a single female need to
release only a billionth of an ounce per second to
attract every male silkworm moth within a mile.
Human ears are most sensitive to sound
frequencies that include human voice consonants
and a baby’s cry.
Absolute Thresholds

Absolute threshold:


the lowest level of a stimulus
detected half the time


Example: Why do dogs go crazy when you blow into
a dog whistle?
Can you image if our auditory absolute threshold was
lower than it is?
Absolute Thresholds

Absolute thresholds can vary across
individuals

Limitations and variances




Age
Abilities
Experiences
Fatigue: Life and death implications
© 2008 The McGraw-Hill Companies, Inc.
Difference Thresholds

Detection of change or
discrimination between stimuli

JND:



smallest difference between two stimuli
detected half the time
JNDs vary from person to person and
by sense
Difference Thresholds


Weber’s Law:
For a person to notice change:
Difference threshold is not a
constant amount, but some
constant proportion of the
stimulus.
Example: May notice that a 2 liter of
Coke is on sale for $1 less, but would
not notice if a car was on sale for $1
less.

Sensory Adaptation

Sensory Adaptation


responsiveness to stimuli diminishes
with repeated exposure
Smell adapts quickly



Ex) Being on a farm or an ethnic
restaurant.
Ex) Jumping into a cold pool
Ex) Ring or watch
Vision prevents adaptation
Our eyes are constantly quivering!

Signal Detection Theory

Predicts when and how we will detect the
presence of a faint signal with background
noise.

There is no single absolute threshold

Depends on participants experience,
expectations, motivation, and level of fatigue.
© 2008 The McGraw-Hill Companies, Inc.
Signal Detection Theory
Factors Affecting Perception

Attention




Stroop Effect



Selective attention
Cocktail party effect
Novelty, size, color, movement
Reading is highly practiced, automatic activity
Bottom-up processing (stimulus-driven)
Sensory Adaptation
9/28
In addition to trying the activity below, have your homework out
Subliminal Stimulation


We can unconsciously sense subliminal
(literally “below threshold”) stimuli.
Ex. 1956 report of NJ movie audiences
being influenced by subliminal messages.
Unwittingly influenced?!?




Only has a subtle, fleeting effect
Anthony Greenwald experiment (tapes with
self esteem or memory)
16 double blind experiments and all proved
to be ineffective
Priming=predisposing one’s perception,
memory, or response by a previous
association.
Vision


Transduction: conversion of one form of
energy to another
in sensation, transforming of stimulus
energies into neural impulses (ex: light
energy into neural messages)
© 2008 The McGraw-Hill Companies, Inc.
Sensation Chart
Sense
Stimulus
Receptors
Vision
Electromagnetic
energy
Rods and cones in
retina
Hearing
Sound waves
Hair cells of the
inner ear
Smell
Chemical
Substances in air
Receptor cells in
the nose
Taste
Chemical
Substances in
saliva
Taste buds
Touch
Pressure on skin
Nerve Endings
Threshold
Vision

What strikes
our eyes is not
color, but
pulses of
electromagnet
ic energy that
are visual
system
perceives as
color.
© 2008 The McGraw-Hill Companies, Inc.
Vision

2 Physical Characteristics that help
determine our sensory experience.




Wavelength= distance from wave peak to the
next.
Determines the Hue=or color we experience.
Amplitude=Height of wave
Determines the intensity=the amount of energy
in light waves.
Wavelength and Amplitude
© 2008 The McGraw-Hill Companies, Inc.
Processing Light



Color is produced/created by the nervous system in
response to wavelengths
Color is determined by an absorption certain wavelengths
Wavelengths





Short  violet
Midlength  green, blue, yellow
Long  red
Average person can discriminate about two million
different colors
Photoreceptors


Rods—black, white, gray
Cones—colors
© 2008 The McGraw-Hill Companies, Inc.
Differing Eyes

Bee detects reflected ultraviolet wavelengths
Getting the Light into the Eye
Mirror image is inverted……we don’t see image as a
whole, but receptor cells convert light energy into neural
pulses. Impulses are sent to the brain to be perceived
and processed.
Acuity=sharpness in vision can be affected by
small distortions in the eye’s shape.
Nearsighted
Farsighted
Converting Light into Images


From here conversion is continued by
photoreceptors in the retina.
Two main types of photoreceptors: Rods
and cones.
36
Rods and Cones


They contain photopigments – chemicals
that respond to light.
Light triggers action potentials in
photoreceptors (rods and cones) by breaking
down photopigments.
37
Rods and Cones

Rods unable to
discriminate color.



But more sensitive to
light than cones.
Three forms of
pigments in cones
provide the basis for
color vision.
Rods and cones differ
in their distribution in
the eye.
Cone = Color
38
Distribution of rods and
cones
•Cones are concentrated in the fovea or
center of the retina
•We have greatest visual acuity in the center
of our field of vision because we have the
most cones there.
•There are no rods in the human fovea.
•The number of rods increases as we move
away from the fovea to the outer parts of the
retina. * This is why our pupils dilate
•Rods are more sensitive to light than cones,
so you can see dim light better just outside of
39
your central field of vision.
Figure 4.10: Cells in the
Retina
40
Cells in the retina – that help rods and
cones send signals to the brain



Light energy striking the rods and cones produces chemical
changes that generate neural signals.
These signals activate neighboring bipolar cells which activate
Ganglion Cells – they sum up the signals from the rods and
cones and send action potentials through the optic nerve and to
the brain.
The axons from the network of Ganglion Cells converge like the
strands of a rope to form an Optic Nerve= passage way to the
visual cortex through the thalamus
41
Figure 4.14: Pathways from the Ganglion
Cells into the Brain
42
Visual Information processing





Info. From the retina’s nearly 130 million receptor rods & cones is
received and transmitted by the million or so ganglion cells, whose
axons make up the optic nerve, which shoots info. To the brain.
Any given retinal area relays its info.to a corresponding location in the
occipital lobe.
This sensitivity can also lead to misfires, however.
Try this: Turn your eyes to the left, close them, and then gently rub the
right side of your right eyelid with your fingertip. Note the patch of
light to the left, moving as your finger moves.
This is because your retinal cells are so sensitive that even pressure
triggers them to relay information.
© 2008 The McGraw-Hill Companies, Inc.
Blind Spot?
Where the optic nerve leaves the eye
(there are no receptor cells)
Figure 4.16: The Color Circle
45
Trichromatic or YoungHelmholtz Theory of Color
Vision


Any color can be produced by mixing pure
lights of blue, green, and red.
There are three types of cones, each most
sensitive to particular wavelengths.
46
Figure 4.18: Relative Responses
of Three Cone Types to Different
Wavelengths of Light
47
Problem with the Trichromatic
Theory



Cannot explain some aspects of color
vision, such as afterimage.
Color blind can often see yellow when
mixing red and green (no red cones)
Example: Stare at the dot on the next slide
for thirty seconds.
48
Opponent-Process Theory of
Color Vision

Visual elements sensitive to color are
grouped into three pairs.



Members of each pair oppose, or inhibit,
each other.
Three pairs are a red-green element, a blueyellow element, and a black-white element.
Explains color afterimages and the
phenomenon of complimentary colors.
49
Figure 4.20: Color Coding and
Ganglion Cells
52
Present Solution to Color
Vison Mystery

1.
2.
Two stages:
Retina’s red, blue, and green cones
respond in varying degrees to different
color stimuli (young-helmholtz
trichromatic theory).
Signals are then processed by the nervous
system’s opponent-process cells on the
way to the visual cortex.
© 2008 The McGraw-Hill Companies, Inc.
Colorblindness



If you only have 2
photopigments in
your cones you
will be color blind
(usually lack red
or green cones).
Do you see a
number in the
image on the
right?
Some women have
4 photopigments…
super color vision.
54
Hearing-Auditory Processing
© 2008 The McGraw-Hill Companies, Inc.
Audition- The Ear

Middle Ear


Inner Ear


chamber between eardrum and cochlea containing
three tiny bones (hammer, anvil, stirrup) that
concentrate the vibrations of the eardrum on the
cochlea’s oval window
innermost part of the ear, containing the cochlea,
semicircular canals, and vestibular sacs
Cochlea

coiled, bony, fluid-filled tube in the inner ear
through which sound waves trigger nerve impulses
Perceiving Pitch


Place Theory – best explains how we sense high pitches

the theory that links the pitch we hear with the place where the
cochlea’s basilar membrane is stimulated
Frequency Theory – best explains how we sense low pitches

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.
*Problem with high pitched sounds (neurons can not fire faster than
1000 times per second. Volley Principle
How We Locate Sounds



Sound waves will strike
one ear sooner and more
intensely than the other
allowing us to locate
sound
This is why we tilt our
head to one side when
trying to pinpoint a
sound.
Sound travels at 750
miles per hour and our
ears our ~6 inches apart,
so the difference is small,
but our brain can pick up
on this.
Hearing Loss

Conduction Hearing Loss

hearing loss caused by damage to the
mechanical system that conducts sound waves
to the cochlea


Ex: eardrum punctured, damage to the tiny bones
that vibrate
Sensorineural Hearing Loss – more common

hearing loss caused by damage to the cochlea’s
receptor cells or to the auditory nerve


Also called nerve deafness
Can be due to a disease, but more commonly from
heredity, aging, and prolonged exposure
Deafness
Sensorineural Deafness
Conduction Deafness


Something goes wrong
with the sound and
vibration on the way to
the cochlea.
You can get a hearing
aid to help.




The hair cells in the cochlea
get damaged.
Can be caused by loud noises
NO WAY to replace the hairs.
Cochlea implant is possible.
Perceptual Constancy

Perceptual Constancy: The tendency to
perceive objects as relatively stable despite
continually changing sensory information.

Examples:

Shape, size, color, brightness

Varying distances, lighting conditions, angles
© 2008 The McGraw-Hill Companies, Inc.
Hearing Loss

Amplitude required for
perception relative to
20-29 year-old group
Older people tend to hear low frequencie
well but suffer hearing loss for high
frequencies
High frequency
Results from nerve
Degeneration near
The beginning of
The basilar
Membrane. This
Supports the
Place Theory!
1
time
10
times
100
times
1000
times
32 64 128 256 512 1024 2048 4096 8192 16384
Frequency of tone in waves per second
Cochlear Implants


A way to restore
hearing for people
with nerve deafness.
Translates sound into
electrical signals that,
wired into the
cochlea’s nerves,
convey some
information about the
sound to the brain.
© 2008 The McGraw-Hill Companies, Inc.
Cochlear Implants and Deaf
Culture




Many parents want their children to experience the
world of sound and talk.
Do not wait for child’s consent because it would
not make the implant as effective
Deaf culture advocates object to using cochlear
implants before they can speak because they do
not view deafness as a disability.
They do not believe that signing shows a linguistic
disability.
© 2008 The McGraw-Hill Companies, Inc.
Touch




Energy detected is physical
pressure on tissue.
Many nerve endings in the skin
act as touch receptors.
Touch is both an active and
passive sense.
Changes in touch provide most
important sensory information.
66
Coding of Touch Information

Intensity of the stimulus is coded by:



Firing rate of individual neurons and
The number of neurons stimulated.
Location is coded by the location of the
neurons responding to the touch.
67
Pain





Pain provides information about impact of
world on body.
Information-carrying aspect of pain very
similar to that of touch and temperature.
Two types of nerve fibers carry pain signals
from skin to the spinal chord.
Pain pathways
Cerebral cortex plays role in the experience
of pain.
68
Figure 4.25: Pain Pathways
69
Modulating Pain




Gate Control Theory – There is a “gate” like function in the spinal cord that
can let pain signals through to the brain or not. –
Spinal cord contains small nerve fibers that conduct most pain signals and
large nerve fibers that conduct most other sensory signals
Rubbing the skin around a wound can cancel out some pain signals (stimulate
large nerve fibers and block some of the pain messages)
Pain gate can be closed by information from the brain (you can be distracted
from pain).
70
The Chemical Senses

Olfaction detects airborne chemicals
(Olfactory System)


Our sense of smell
Gustation detects chemicals in solution that
come into contact with receptors inside the
mouth (Gustatory System)

Our sense of taste
71
Smell, Taste, and Flavor




Smell and taste act together to form system
known as flavor.
Tastes and odors can prompt strong
emotional responses.
Nutritional state can affect taste and flavor
of food and motivation to eat particular
foods.
Flavor includes other characteristics of
food.
72
Gustation



Taste receptors are in the taste buds… they are
groups of cells called papillae (pores that catch
food chemicals)
Different papillae code more strongly for sweet,
sour, bitter and salty. They respond to two or
three, but code most strongly for one.
Two additional taste sensations, umami
enhances other tastes (MSG/meaty) and
astringent which is a “dry” sort of taste found in
red wine and some teas.
73
There are several types of
papillae
74
Are you a super taster?




Lets find out…. Draw a simple blank map of the tongue
From http://www.thetech.org/genetics/supertaster.php
Swab the blue food coloring on the front of the tongue (cover the tip
and about 1/2 inch back). Have the subject move the tongue around in
the mouth and swallow. This distributes the dye. Swallowing the dye is
not hazardous. You will see pink circles emerge from the blue
background. The pink circles are the fungiform papillae. The
fungiform papillae appear pink because they do not stain.
Now use the hole-punched cards to take 4 or 5 samples from your
partner’s tongue. Count how many papillae you find in the circle. Map
these areas on your tongue drawing. What is the average number of
papillae per sample?
75
Are you a supertaster?
>30 papillae
8 papillae
76
A few facts….





Taste receptors replace themselves every week or two (smoking and
alcohol will accelerate the decline in taste buds!)
Our emotional responses to taste our hardwired.
People without tongues can still taste…through receptors in the back
and on the roof of the mouth.
If you lose taste sensation on one side of your tongue, you wouldn’t
notice because the other side will become supersensitive and
compensate.
We can not taste or smell nutrients (fat, protein, starch….sugar,
however….of course we can sniff that one out!)
© 2008 The McGraw-Hill Companies, Inc.
© 2008 The McGraw-Hill Companies, Inc.
Sensory Interaction


Principle that one sense may influence
another.
Smell plus texture plus taste equals flavor
(love apple pie a la mode for this reason)
© 2008 The McGraw-Hill Companies, Inc.
Figure 4.23: The Olfactory
System
80
Olfactory System




Employs about 1,000 different types of
receptors tied straight to Olfactory Bulbs.
Only sense that does not send its messages
through the thalamus.
Processing in several brain regions
including frontal lobe, hypothalamus and
amygdala.
Strong relationship between olfaction and
emotional memory
81
Pheromones

Chemicals released by one animal, and when
detected by another, can shape the second
animal’s behavior or physiology.



Ants, termites use for navigation
Often involved in mating behavior
Role of pheromones in humans not clear.



Vomeronasal organ detects pheromones
May or may not be very active in humans
Seems to detect some hormones
82
Kinesthesia

Sense that indicates where the parts of the
body are with respect to one another.



Necessary guide for movement.
Kinesthetic information comes primarily
from the joints as well as muscles.
Close your eyes and wave your arms around
a bit… now touch your right and left index
fingers together.
83
Vestibular Sense


Organs:

Vestibular sacs

Otoliths- crystals that
stimulate nerves in
vestibular sacs.

Semicircular canals
Neural connections to:

The cerebellum

The autonomic nervous
system (digestive…)

The eye muscles – turn
your head…
84
Gestalt Psychology







Gestalt: A German word meaning “form” or “whole”..
Example with Necker Cube (seeing a “whole” or “form”)
Looks at how we GROUP objects together.
Proximity-group objects that are close together
Similarity-group objects similar in appearance
Continuity-group objects that create a continuous form
Closure-we fill gaps to complete an object (like top-down
processing)
I _ant ch_co_ate ic_ cr_am.
Figure-Ground
The ability to distinguish an
object from its background
Ex. As you read, the words are
the figure and the white paper
is the ground.
Depth Cues
• Visual Cliff Experiment
• Babies refused to go
over the cliff
• We see depth by using
two cues that
researchers have put in
two categories:
• Monocular Cues
• Binocular Cues
Binocular Cues
• We need both of our eyes to use
these cues.
• Retinal Disparity-Our eyes
receive slightly different images
because they are 2 ½ inches
apart. The brain compares these
two images. Disparity becomes
less as distance increases. Ex.
The floating finger sausage.
• Convergence-A neuromuscular
cue caused by the eyes’ greater
inward turn when they view a
near object.The greater the
inward strain, the closer the
object.
Monocular Cues
• You really only need
one eye to use these
(used in art classes to
show depth).
• Linear Perspective
• Interposition
• Relative size
• Texture gradient
• Shadowing
The Mueller-Lyer Illusion
Illusions

Depending on the
direction of the arrow



Inward or outward
Two equal length lines
One appears longer
© 2008 The McGraw-Hill Companies, Inc.
The Visual Cliff


Experiment to test depth
perception in infants
Found that infants early on
could perceive depth


Older infants would not
crawl on “deep” side
Younger infants showed
physiological changes
© 2008 The McGraw-Hill Companies, Inc.
Form Perception

The process by which sensations are
organized into meaningful shapes and
patterns.

The figure-and-ground principle

brain organizes sensory input into:



a figure (the center of attention)
ground (the background)
Rubin’s characteristics

“Thinglike”

In front of ground

Dominates, more memorable
© 2008 The McGraw-Hill Companies, Inc.
Laws of Grouping

Similarity- Group together stimuli that are similar

Proximity-Group together stimuli that are together

Continuity-Perception of contours or straight lines as
continuous

Closure- Tendency to close figures gaps in a figure and
perceive it as whole.
© 2008 The McGraw-Hill Companies, Inc.
Laws of Grouping: Demos
© 2008 The McGraw-Hill Companies, Inc.
Operational Definition?

also called functional definition, defines something (e.g. a variable, term, or
object) in terms of the specific process or set of validation tests used to
determine its presence and quantity.
EXAMPLES:
An operational definition describes exactly what the variables are and how they
are measured within the context of your study. For example, if you were doing a
study on the impact of sleep deprivation on driving performance, you would need
to operationally define what you mean by sleep deprivation and driving
performance.
In this example you might define sleep deprivation as getting less than seven hours
of sleep at night and define driving performance as how well a participant does on
a driving test.
© 2008 The McGraw-Hill Companies, Inc.