AP Psychology
Sensation and Perception
Alice F. Short
Hilliard Davidson High School
Unit 3, Chapter 4
Sensation and Perception
• sensation – the process of receiving stimulus
energies from the external environment and
transforming those energies into neural energy
– Relate to sensitive – 1.having the power of sensation,
2. responsive to or aware of feelings, moods,
reactions, etc., 3. easily irritated; delicate: sensitive
skin, 4. affected by external conditions or stimuli
• perception – the process of organizing and
interpreting sensory information so that it has
meaning
– Relate to perceptive - having or showing keenness of
insight, understanding, or intuition:
Sensation and Perception
• sensory receptors  thalamus  specific
parts of the cerebral cortex
• sensation and perception = unified
information-processing system
Bottom-up vs. Top-down Processing
• bottom-up processing – the operation in sensation and
perception in which sensory receptors register
information about the external environment and send
it up to the brain for interpretation (part to whole)
– song for first time
• top-down processing – the operation in sensation and
perception, launched by cognitive processing at the
brain’s higher levels, that allows the organisms to sense
what is happening and to apply that framework to
information from the world (whole to part)
– favorite song
What do you see?
Predator vs. Prey
Categories of Sense Organs and
Sensory Receptors
• sensory receptors – specialized cells that detect
stimulus information and transmit it to sensory
(afferent) nerves and the brain
• photoreception – detection of light
– perceived as sight
• mechanoreception –detection of pressure
vibration, and movement
– perceived as touch, hearing and equilibrium
• chemoreception – detection of chemical stimuli
– perceived and smell and taste
Sensory Receptors
Name the category for each (photoreception,
mechanoreception, or chemoreception)
Festive Disease for the Senses
• synaesthesia – an experience in which one
sense (say, sight) induces an experience in
another sense (say, hearing)
– Possible Outcomes: see music, taste color
– (seen in Criminal Minds, Season 8 “Magnificent
Light”)
Another Festive Disease for the Senses
• phantom limb pain –pain / felt movement of
lost limb
– Mirror therapy
Thalamus
• thalamus = relay station for brain (nearly all
sensory information pass though the
thalamus)
– brain = complex (multiple pathways)
Absolute Sensory Thresholds
• The foolish definition of absolute threshold –
the minimum amount of stimulus energy that
person can detect (50 percent of the time)
Noise
• noise – term given to
irrelevant and competing
stimuli—not just sounds
but any distracting
stimuli for our senses
Difference Threshold
(a.k.a. Just Noticeable Difference)
• difference threshold – the degree of
difference that must exist between two stimuli
before the difference is detected
• Weber’s law – the principle that two stimuli
must differ by constant minimum percentage
(rather than a constant amount) to be
perceived as different
Subliminal Perception
• subliminal perception – the detection of
information below the level of consciousness
– Challenges the usefulness of the idea of
thresholds
– Read and discuss p. 103, Psychological Inquiry:
“Subliminal Perception: Working Up a Thirst”
Signal Detection Theory
• signal detection theory –a theory of
perception that focuses on decision making
about stimuli in the presence of uncertainty
– individual variations
• How are you feeling?
– contextual variations
• What is the urgency of the situation?
Signal Detection Theory
• information acquisition – the information you
can assess
• criterion – the basis for making a judgement
from available information
Signal detection theory
Perceiving Visual Stimuli
• attention
• perceptual set
Perceiving Sensory Stimuli: Attention
• attention – the process of focusing awareness
on a narrowed aspect of the environment
– selective attention – the process of focusing on a
specific aspect of experience while ignoring others
– cocktail party effect (hearing specific voice)
– Stroop effect – the way that automatically reading
a color name can make it difficult to name the
color in which the word is printed
Stroop Effect
• Stroop effect – the way that automatically reading a color name can make it
difficult to name the color in which the word is printed (p. 105)
• failure of selective attention
• shiftable
Attention
– Monitoring many things at once
• novel stimuli
– Novel
– Different
– Unusual
• size, color, movement
• emotional stimuli (specific words, etc.)
– emotion-induced blindness – when we encounter an
emotionally charged stimulus, we often fail to recognize a
stimulus that is presented immediately after
• inattentional blindness – failure to detect unexpected
events when our attention is engaged by tasks
– counting basketball passes and gorilla costume (p. 106)
Perceiving Visual Stimuli: Perceptual Set
• perceptual set – a predisposition or readiness
to perceive something in a particular way
– children can be for accurate without solidified
perceptual sets
Sensory Adaption
• sensory adaption – a change in the
responsiveness of the sensory stem based on
the average level of surrounding stimulation
– takes time
– blind right after you turn off lights
– freezing when first in pool
The Visual System
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The Visual Stimulus and the Eye
Visual Processing in the Brain
Color Vision
Perceiving Shape, Depth, Motion and
Constancy
Light
• Light – a form of electromagnetic energy that can be
described in terms of wavelengths.
– Travels though space in waves
– Visible from 400 to 700 nanometers
– Determines hue or color
• Wavelength – the distance from the peak of one wave to
the peak of the next
• Amplitude – the height of the waves
– determines the brightness of the stimulus
• Purity – whether all the waves are the same or different
– Affects perceived saturation
The Structure of the Eye
(p. 111-112)
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Sclera
Iris
Pupil
cornea
Lens
Curvature
Retina
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Rods
• Optic chiasm
Cones
• Visual cortex
Fovea
Bipolar cells
Ganglion cells
Optic nerve
Blind spot
The Structure of the Eye (camera)
(p. 111-112)
• sclera - the white, outer part of the eye that helps to
maintain the shape of the eye and to protect it from injury
• iris – the colored part of the eye
• pupil – the opening in the center of the iris; appears black
• cornea – clear membrane just in front of the eye
– Bends light falling on the surface of the eye just enough to focus it
at the back (brings image into focus)
• lens – a transparent and somewhat flexible disk-shaped
structure filled with a gelatin-like material
– Bends light falling on the surface of the eye just enough to focus it
at the back (brings image into focus)
– Curvature – allows eye to focus on things up close (more curved)
or far away (flatter)
• Ability to curve decreases with age (thus stylish reading glasses)
The Structure of the Eye (film)
• retina – the multilayered light-sensitive surface in the eye
that records electromagnetic energy and converts it to
neural impulses for processing in the brain (primary
mechanism for sight)
– rods – the receptor cells in the retina that are sensitive to light
bun not only very useful for color vision
• Found almost everywhere on the retina except the fovea
• Gives ability to detect fainter spots of light on the peripheral
– cones – the receptor cells in the retina that allow for color
perception
– fovea – a tiny area in the center of the retina at which vision is
at its best
• contains only cones
• explains difficulty of reading out of corner of eye
Structure of the Eye
• (p. 112 of textbook)
Structure of the Eye: Retina
The Structure of the Eye
• retina  bipolar cells  ganglion cells (axons = optic
nerve
• bipolar cells –
• ganglion cells –
• optic nerve – the structure at the back of the eye,
made up of axons of the ganglion cells, that carries
visual information for further processing
• blind spot – the place on the retina where the optic
nerve leaves the eye on its way to the brain
– cannot see anything that reaches only this part of the
retina
– brain uses top-down processing to to “fill in the gaps”
The Visual Processing in the Brain
• eyes = beginning of visual perception
• brain = sent neural impulses for analysis and
integration
• optic chiasm – point in brain where the optic
nerve fibers divide, and approximately half of
the nerve fibers cross over the midline of the
brain
Visual Processing
(p. 114)
• visual information
originating in the right
halves of the two retinas
(from the left visual field)
is transmitted to the right
side of the occipital lobe
in cerebral cortex; left
half of retinas (right
visual field) to left
occipital lobe
The Visual Cortex
• visual cortex – most visual information is sent
here before moving to other visual areas for
further analysis
– located in occipital lobe
– is the part of cerebral cortex involved in vision
• feature detectors – neurons in the brain’s
visual system that respond to particular
features of a stimulus
The Visual Cortex:
David Hubel and Torsten Wiesel (1963)
• won Nobel Prize for research on feature detectors (in
cats)
– recorded activity of a single neuron in a cat while it looked
at patterns that varied in size, shape, color , and
movement
– found that the visual cortex has neurons that are
individually sensitive to different types of lines and angles
– Noted that when deprived of certain types of visual
stimulation early one, kittens lost the ability to perceive
these patterns
• Suggests there might be a critical period in visual development
and that the brain requires stimulation it its efforts to delegate its
resources to different perceptual tasks brain “learns” to perceive
through experience.
Perceiving Shape, Depth, Motion and
Constancy
• contour – a location at which a sudden change
of brightness occurs
• figure-ground relationship – the principle by
which we organize the perceptual field into
stimuli that stand out (figure) and those that
are left over (ground)
– Example: text (figure) on a page (ground)
Figure-Ground Relationship
Gestalt Principles
• gestalt psychology – a school of thought
interested in how people naturally organize their
perceptions according to certain patterns
– main principle: the whole is different from the sum of
its parts -- computer screen image (sum) pixels (parts)
– closure
– proximity
– similarity
– continuity
– law of Pragnanz
• “AP Psych – Gestalt Principles”
Gestalt Principles: Closure
• closure: disconnected or incomplete figures
 fill in the spaces and see them as complete
figures
Gestalt Principles: Proximity
• proximity: object near each other  see them
as a unit (4 columns; not 16 squares)
Gestalt Principles: Similarity
• similarity: objects that are similar  seen as a
unit (columns of circles and squares; rows of
circle and squares)
Depth Perception
• depth perception – the ability to perceive objects
three-dimensionally (binocular and monocular cues)
• binocular cues – depth cues that depend on the
combination of the images in the left and right eyes
and on the way to the two eye work together
– convergence - Binocular cue to depth and distance in
which the muscle movements in our two eyes provide
information about how deep and/or far away something is
• up close  eyes almost crossing
– disparity – difference between the images in the two eyes
to determine the depth or distance of the object
• image “jumps” between eyes
Depth Perception
p. 118
• monocular cues – powerful depth cues available
from the image in one eye, either the right or the
left
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–
–
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familiar size
height in the field of view
linear perspective and relative size
overlap
shading
texture gradient
• Read p. 118. Be prepared to apply terms to image
on next slide.
Monocular Cues:
Shading, Texture Gradient
© 2011 The McGraw-Hill Companies, Inc.
Monocular Cues:
Linear Perspective, Height in Field
© 2011 The McGraw-Hill Companies, Inc.
Motion Perception
p. 119
1. Neurons that are specialized to detect
motion
2. Feedback form our body tells us whether we
are moving or whether some one or some
object is moving
3. The environment we see is rich with cues
that give us information about movement
• apparent movement – the perception that a
stationary object is moving
Perceptual Constancy
• perceptual constancy – the recognition that
objects are constant and unchanging even
though sensory input about them is changing
(size, shape, color)  demonstrates that we
interpret sensation
– size constancy
– shape constancy (door example)
– color constancy
Visual Perception: Motion
© 2011 The McGraw-Hill Companies, Inc.
Auditory System
• The Nature of Sound and How We Experience It
• Structures and Functions of the Ear
– Outer ear
– Middle ear
– Inner ear
• Theories of Hearing
• Auditory Processing in the Brain
• Localizing Sound
The Nature of Sound and How We
Experience It
• sound waves – vibration in the air that are processed
by the auditory (hearing) system
– frequency – the number of cycles (full wavelengths) that
pass through a point in a given time interval
• pitch – the perceptual interpretation of the frequency of a sound
– complex sounds – sounds with numerous frequencies of
sound blending together
• timbre – the tone saturation, or the perceptual quality, of a sound
– Perceptual difference b/w different instruments playing the same note
– amplitude – the amount of pressure the sound wave
produces relative to a standard, typically 0 decibels-measured in decibels (dB)
• loudness – the perception of the sound waves amplitude
Frequency
• low frequency = low pitch
• high frequency = high pitch
• distinguish b/w adult and child
Amplitude
Decibels
Source
Exposure Danger
180
Space shuttle launch
Hearing loss certain within 150
feet of launch pad
140
Jet aircraft motor
Any exposure dangerous
120
Sandblaster, thunderclap
Immediate danger
100
Heavy auto traffic, lawn
mower
2 hours
60
Normal conversation
No danger
40
Quiet office
No danger
30
Quiet library
No danger
20
Soft whisper
No danger
0
Minimal detectable sound
No danger
Volume
Complex Sounds: Timbre
• Timbre -
Structures and Functions of the Ear
• outer ear – the outermost part of the ear,
consisting of the pinna and the external
auditory canal
• middle ear – the part of the ear that channels
sound through the eardrum, hammer, anvil,
and stirrup to the inner ear
• inner ear – the part of the ear that includes
the oval window, cochlea, and basilar
membrane
Structure of the Ear
© 2011 The McGraw-Hill Companies, Inc.
Outer Ear
• pinna (plural, pinnae) – the outer, visible part
of ear
– collections sounds and channels them into the
interior of the ear
– moveable in some animals (localization)
• external auditory canal
Middle Ear
• eardrum (tympanic membrane) – separates the
outer ear from the middle ear
– vibrates in response to sound
• hammer  anvil  stirrup – intricately
connected chain of the three smallest bones in
body
– transmit sound waves to the fluid-filled inner ear (at
oval window) by vibrating
– can amplify sounds or decrease intensity to protect
inner ear (muscles)
Inner Ear
• inner ear – converts sound waves into neural
impulses to send to brain
• oval window – transmits sound waves to the
cochlea (received from stirrup)
• cochlea – tubular, fluid-filled structure, coiled
– basilar membrane – lines the inner wall of the
cochlea and runs its entire length
• tells about frequency, pitch, complexity of sound
• hair cells – ear’s sensory receptors (cilia sprout at top of hair
cells) – delicate  damage can lead to deafness or difficulty
hearing
– tectorial membrane – jellylike flap above hair cells
• generates impulses that the brain interprets as sound
Cochlear Implant
• cochlear implant – a small electronic device that
is surgically implanted in the ear and head
– allows deaf or hard-of-hearing individuals to detect
sound
– more effective the younger implanted
• DISUCSSION: Read Critical Controversy: “Are
Cochlear Implants a “Cure for Deafness” (p. 124)
– answer “What do you think?” questions
– have thoughts 
Theories of Hearing
• place theory – theory on how the inner ear registers the
frequency of sound, stating that each frequency produces
vibrations at a particular spot on the basilar membrane
(better at explaining sounds below 1,000 firing per second)
– high pitch tone – narrow area of basilar membrane at the base
of cochlear
• explained well by theory
– low pitch tone – wide end of cochlea
• explained poorly by theory
• frequency theory – theory on how the inner ear registers
he frequency of sound stating that the perception of a
sound’s frequency depends on how often the auditory
nerve fires
– volley principle – modification of frequency theory stating that
a cluster of nerve cells can fire neural impulses in rapid
succession, producing a volley of impulses
• combination of theories need for sounds above 1,000 times
per second
Auditory Processing in the Brain
• auditory nerve – the nerve structure that
receives information about sound from the
hair cells of the inner ear and carries these
neural impulses to the brain’s auditory areas
(extends from the cochlea to brain
• stem)
– left ear  right side of brain
– right ear  rights side of brain
– temporal lobe
Localizing Sound
• basilar membrane – tells about frequency,
pitch, complexity of sound
– NOTHING to do with location
• Localization:
– sound shadow – caused by the listener’s head,
which forms a barrier that reduces the sound’s
intensity
• timing
• intensity
The Other Senses
• The Skin Senses
– Touch
– Temperature
– Pain
• The Chemical Senses
– Taste
– Smell
• The Kinesthetic and Vestibular Senses
The Skin Senses
• skin – largest sensory system
– cutaneous senses (3 types of receptors):
• touch (mechanical energy / pressure against skin)
• temperature
– thermoreceptors – sensory nerve endings under the skin that
respond to changes in temperature at or near the skin and
provide input to keep the body’s temperature at 98.6 degrees
Fahrenheit (heat = dominant)
• pain (adaptive for survival; intense stimulation of any sense
produces pain)
– prostaglandin – stimulate receptors that cause the experience of
pain (many painkiller reduce production)
– fast pathway  thalamus (fast response required)
– slow pathway  detour in limbic system (tells you to “slow
down” your lifestyle – “nagging pain”)
Pain
• pain (adaptive for survival; intense stimulation of
any sense produces pain)
– prostaglandin – stimulate receptors that cause the
experience of pain (many painkiller reduce
production)
• fast pathway  thalamus (fast response required)
• slow pathway  detour in limbic system (tells you to “slow
down” your lifestyle – “nagging pain”)
– endorphins – neurotransmitters (slow pathway)
– factors: motivation, expectation, decision factors
– women experience more pain
Chemical Senses
• taste (sweet, sour, bitter, salty)
+ umami or yummy or savory (L-glutamate)
– papillae – round bumps above the tongue's surface that
contain the taste buds, the receptors for taste (replaced
every two weeks)
• 10,000 taste buds (younger)
• 5,000 taste buds (older)
• smell
– olfactory epithelium – the lining of the roof of the nasal
cavity, containing a sheet of receptor cells for smell
• unique: neurons replace themselves after injury; don’t pass
through thalamus
•  temporal lobes  various brain regions (including limbic system
– linked to emotion and memory (LOVE!)
– dogs – 100 times lower levels
The Kinesthetic and Vestibular Senses
• kinesthetic (MOP) – movement, orientation, posture
– not in specific organ; embedded in muscle fibers and joints
– same pathways to brain as touch
• vestibular (MB) – movement, balance (begins in auditory
nerve, which contains both cochlear nerve and vestibular
nerve for balance and movement)
– connects to medulla (most), directly to cerebellum, temporal
cortex, or other places (not fully charted)
– vision used in addition (when everything in visual field is
moving… generally WE are moving
– proprioceptive feedback – information about the position of
our limbs and body parts in relation to other body parts
– semicircular canals of inner ear – three fluid-filled circular tubes
that lie in the three plans of the body
• right-left
• front-back
• up-down
Sensation, Perception, and Health and
Wellness
• Take care of yourself! You don’t regenerate.
THE END!