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Devil’s Tuning Fork
Sensation and Perception
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Basic Principles
 Sensation
 The process of receiving stimulus energies from the external
environment
 Transduction
 The process of transforming physical energy into
electrochemical energy (action potential)
 Perception
 The process of organizing and interpreting sensory information
© 2008 The McGraw-Hill Companies, Inc.
Perceiving Sensory Stimuli: First Step
You have to PAY ATTENTION!
 Selective Attention – you choose to pay attention to some
stimuli over others
 Inattentional blindness – we miss background information
when we heavily concentrate on one thing (gorilla
experiment)
 Change Blindness – we are blind to subtle changes in the
scope of a larger picture (door study)
 http://www.simonslab.com/videos.html
Perceiving Sensory Stimuli: First Step
You have to PAY ATTENTION!
 Cocktail party effect – we filter out irrelevant info while
focusing on one important item – but we still process all
the info in case something relevant is happens
Selective Attention – Dichotic
listening task
When receiving info in
both ears we can
choose to pay
attention to only one
side – and will
ALMOST completely
ignore the other side
Sensory Thresholds
 Absolute Threshold
 The minimum amount of energy an organism can detect
50% of the time
 Noise – Irrelevant and competing stimuli
Approximate Absolute Thresholds for Humans
Sensory Modality
Absolute Threshold
Vision
Candle flame seen at 30 miles on a clear, dark night
Hearing
Tick of a watch under quiet conditions at 20 feet
Taste
1 teaspoon of sugar in 20 gallons of water
Smell
1 drop of perfume diffused into the entire volume of
a large apartment
Touch
Wing of a fly or bee falling on a person’s cheek from
a distance of 1 centimeter
© 2008 The McGraw-Hill Companies, Inc.
Source: Based on Galanter, 1962.
Weber’s Law
 Two stimuli must differ by
a constant minimum
percentage (not a
constant amount) to be
perceived as different
 Also known as the just
noticeable difference
signal detection theory
 Proposes that the detection
of stimuli involves a
decision process as well as
a sensory process, which
are both influenced by a
variety of factors besides
stimulus intensity.
 Examples
 Radar
 Pizza Guy
Perceiving Sensory Stimuli:
Cognitive Helping Processes
 Perceptual Set: Predisposition/readiness to see something
a particular way
Cognitive Helping Processes:
Perceptual Set
 What is seen in the center figures depends on the order
in which one looks at the figures:
 If scanned from the left, a man’s face is seen.
 If scanned from the right, a woman’s figure is seen.
Stroop Experiment
Stroop Experiment
Sensory Adaptation
 Diminished sensitivity as a result of constant stimulation
 Can you feel your underwear?
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
Photoreception (Vision)
Detection of light
Mechanoreception (Touch, Hearing)
Detection of pressure, vibration, and
movement
Chemoreception (Smell and Taste)
Detection of chemical stimuli
© 2008 The McGraw-Hill Companies, Inc.
Our TEN senses!
 Vision
 Cold
 Pain
 Smell
 Hearing
 Vestibular
 Hot (warm)
 Pressure
 Taste
 Kinesthesis
Structure of the Eye
Cornea – protects the eye
Pupil – controls amount of light
Iris – colored part of eye
(controls light too)
Lens – focuses the image
Retina – contains photo receptors
Fovea – contains mostly cones –
best vision
Structure of the Eye: Retina
© 2008 The McGraw-Hill Companies, Inc.
 Rods
 Black and white vision
 Function well in low
illumination
 Humans have ≈ 120 million
rods
 Cones
 Color vision
 Operate best under high
illumination
 Humans have ≈ 6 million
cones
Characteristics of Light
 Wavelength
 (hue)
 Intensity
 (brightness)
 Complexity
 (purity or saturation)
 It all ends with the “color” we see.
Visual Processing
 Pathway of visual information
 Optic Nerve  Optic Chiasm Visual
Cortex
 Optic Chiasm: Optic nerve fibers divide
 Left Visual Field  Right Hemisphere
 Right Visual Field  Left Hemisphere
 Primary visual cortex
 Occipital lobe
 Initial visual processing
Two classic theories of color vision:
1:Young-Helmholtz trichromatic theory: three types of
cones, blue, green, red
The ratio of activity in the
three types of cones
yields our experience of
a particular hue, or color.
 Color Blindness
 + Trichromats: people with normal color vision
 + Dichromats: color-blind in one cone
 deficient in the blue-yellow system, the red-green system, or both. (Approximately 7% of the
male population and 1% of the female population are dichromats.)
 + Monochromats: sensitive only to the black-white system,
totally color-blind.
Monkeys Get Full Color Vision:
ScienceNews.org
 Squirrel monkeys with red-
green color blindness were
given gene therapy
 20 weeks able to see
differences on color blindness
tests
 Effects stable after 2 years
 What does this mean for
people?
 Disorienting effects
• Are they experiencing color or
different shades of yellow and
blue?
Two classic theories of color vision:
2: Opponent-process theory (red-green and blue-yellow cones)
Hering’s opponent-process theory also
assumed that there are three different
receptors: one for blue-yellow, one for
red-green, one for black-white.
Each of the receptors can function in
two possible ways, depending on the
wavelength of the stimulus.
Again, the pattern of activity in the
receptor yields our perception of the
hue.
Structure of the Eye: Retina
© 2008 The McGraw-Hill Companies, Inc.
Feature Detectors: Hubel & Wiesel
 Highly-specialized cells in the visual cortex
 Size, shape, color, movement, or combination
 Deprivation studies: brain “learns” perception
Structure of the Ear
Pinna
Auditory canal
Tympanic membrane (ear
drum)
Middle Ear Bones
Hammer
Anvil
Stirrup
Cochlea
Pathway of Auditory Information
Cochlea  Auditory Nerve ->Thalamus  Temporal Lobe
Most information crosses to other hemisphere
Introductory Psychology Concepts : Hearing
Hearing

Transduction of sound waves
The waves produced by different stimuli are transmitted—usually through
the air — in different patterns, with lower frequencies indicated by fewer
peaks and valleys per second.
Lower frequency
(lower pitch)
(Source: Seeley, Stephens, & Tate, 2000.)
© 2008 The McGraw-Hill Companies, Inc.
Higher frequency
(higher pitch)
Properties of Sound

Wavelength
 Distance between peaks
 Perceived as pitch

Amplitude
 Height of wave
 Perceived as loudness

Timbre
 Mixture of wavelengths; complex sounds
 Perceived as tone saturation
© 2008 The McGraw-Hill Companies, Inc.
How do we locate sounds?
Hearing
 Perception of Sound
•
Place theory of pitch perception:
The specific point in the cochlea where the fluid wave peaks and most strongly bends the
hair cells serves as a frequency coding cue.
Varying frequencies
stimulate different areas
of the basilar membrane.
High-frequency waves
peak quickly and
stimulate the membrane
close to the oval window.
Hearing
 Perception of Sound

Frequency Theory of Pitch Perception:
Nerve impulses sent to the brain match the frequency of the sound wave.
 Both Frequency and Place Theories are applicable in their own ways.
• At low frequencies:
Frequency Theory best explains sound wave frequency coding.
 At higher frequencies:
Place Theory best explains the frequency of a sound wave coding.
Hearing
 In the United States alone, more than 20 million people suffer
from impaired hearing.

They suffer from two major types of hearing loss:
 Conduction Hearing Impairment
• Problems with the mechanical system that transmits sound waves to the cochlea
 Nerve and Hearing Impairment caused by:
• Damaged inner ear receptors or
• Damage to the auditory nerve itself
Noise Pollution
Lengthy exposure of 90 db causes permanent damage
110 db for 30 minutes causes permanent damage
120 db for 5 minutes causes permanent damage
Hearing test
Presbycusis
 Presbycusis
 Age related hearing loss
 Mosquito Ring Tone
Skin Senses (still talking about
mechanoreceptors)
 Body’s largest sense receptor system
 Receptors for this system are located throughout the body
Pain:
 Pain Receptors
 Mechanical, heat, chemical receptors
 Fast and slow pain pathways
 Gate-Control Theory of Pain
 We have a “gate” to control the amount of pain experienced
 Pain Control
 Distraction, focused breathing, and counter-stimulation
© 2008 The McGraw-Hill Companies, Inc.
Acupuncture
 Stimulation-produced
analgesia
 Presumably, the needles
stimulate nerve fibers that
lead to a closing of the pain
gate.
Kinesthesis & Vestibular
 Kinesthetic System
 Structures distributed throughout body that sense
position and movement of body parts.
 Vestibular System
 The inner ear and brain structures that afford a sense
of equilibrium.
 Semicircular canals
 Balance sensitivity &
integration of senses
Chemo Receptors
Other Senses: Chemical
 Taste (gustation)
 Receptors on tongue: papillae
 Four taste qualities: sweet, sour, bitter, salty
 Also have umami (savory)
Other influences may be smell, temperature or “touch”
Other Senses: Chemical
 Smell
 Olfactory epithelium
 By-passes temporal lobe and goes straight to the limbic system
 Use in Humans?
Pheromones
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
Major histocompatibility complex (MHC)
Perception
Bottom-up processing
Perception that consists of the progression of recognizing and processing information
from individual components of a stimuli and moving to the perception of the whole.
Top-down and bottom-up processing occur simultaneously and interact with each
other in our perception of the world around us.
Bottom-Up Processing
Parts Whole
Sensation  Perception
BOTTOM-UP PROCESSING
Top-down Processing
Whole Parts
Perception  sensation
TOP-DOWN PROCESSING
Combination and interpretation of “whole”
Concept, Expectation
Breakdown/analysis of stimuli
Guides, analysis
Detection of individual stimulus elements
Interpretation of incoming stimuli
Perceptual organization
 The whole is greater than the sum of its parts
 Gestalt Psychology
Figure Ground
The tendency to
organize the visual
field into objects
(figures) that stand
apart from
surroundings (back
ground)
Would you trust this face?
Visual Perception: Shape
Principles of Gestalt:
Closure – tendency to
mentally fill in gaps
Proximity – tendency to mentally group objects
together that a near each other
Similarity – tendency to mentally group
objects together that look similar
Continuity
Visual Capture
 The tendency for
vision to dominate
your senses.
 At an IMAX movie, it
feels like you are
moving because it
looks like you are
moving. Your vision
dominates over your
vestibular system.
Monocular cues (one eye only)
 Interposition (overlap) – items overlapping appear closer
 Relative size – if two objects are normally similar in size, the
one that is smaller appears further away
 Relative clarity – hazy objects seem further away
 Relative height – things higher in the field of vision appear
further away
 Linear Perspective – parallel lines appear to converge with
distance
Linear Cues: Ponzo Illusion
Binocular Cues
 The brain constructs perception of 3D from 2D images
processed by the retina
 Binocular Cues
 Disparity – image is cast slightly different on each retina,
location of image determines depth
 Convergence – eyes strain more looking inward as objects draw
nearer
Depth and Dimension
 Devised by Eleanor Gibson
and Richard Walk to test
depth perception in infants
and animals.
 Provides visual illusion of a
cliff.
 Caregiver stands across the
gap.
 Babies are not afraid until
about the age they can crawl.
Psychology, 4/e by Saul Kassin ©2004 Prentice
Hall
The Visual Cliff
Visual Perception: Constancy
 Perceptual Constancies
 Recognition that objects do not physically change despite
changes in sensory input
 Size, Shape, and Brightness Constancies
 Constancies are mediated by experience, binocular cues, and
monocular cues
Motion Perception
How does the brain recognize an object is moving?
How does it interpret the direction of movement?
Brain interprets shrinking
objects as receding and
enlarging objects as
approaching
Visual Perception: Motion
Stroboscopic Effect
the perception of motion produced by
a rapid succession of slightly varying
images (animation, movies)
Stroboscopic effect
Phi phenomenon
an illusion created when two or more
adjacent lights blink on and off in
succession, creating the perception of
movement (lighted signs, illusions)
Other Visual Illusions!
Müller-Lyer Illusion
Horizontal-Vertical Illusion
Linear Perspective: Devil’s Tuning
Fork
98
99
100
Test Image #1
101
Test Image #2
Test Image #4: Reduce size
102
103
Test Image #2 again
Opponent Processes