Download UNIT 4: Sensation and Perception I. Overview A. Sensation

UNIT 4: Sensation and Perception
I.
II.
Overview
A.
Sensation – receiving information through the senses
B.
Perception – compiling the sense information into an idea – usually recognizable
Sensing the World: Some Basic Principles
A.
What are sensation and perception? What do we mean by bottom-up processing and top-down
processing?
1.
Sensory analysis that starts at the entry level as “bottom-up processing”
2.
Experience and expectations are referred to as “top-down processing”
3.
Humans construct perceptions drawing both on sensations and experience and expectations
4.
Example – painting with hidden faces
a.
Bottom-up processing enables sensory systems to detect lines, angles, and colors
b.
Top-down processing analyzes color, apprehensive facial features, etc. for meaning
B.
Selective Attention
1.
How are we affected by selective attention?
a.
The mind selects information from senses to process
b.
Would not be able to process everything at once
c.
Cocktail party effect – ability to attend to one voice among many
2.
Selective attention and accidents
a.
We cannot attend to two things at once
b.
Attention shifts back and forth – does not divide
c.
Hence, texting causes accidents
3.
Selective inattention
a.
Inattention blindness – with attention directed elsewhere, most people do not see
what they are not paying attention to
i.
Focused on counting basketball passes by one of the 3-person teams, they
do not notice the gorilla in the group
b.
Change blindness – something may interrupt what they are paying attention to, but it
will go unnoticed
i.
A big Coke bottle may disappear, a railing may rise, clothing color may
change; none are noticed
c.
Change deafness – similar to change blindness; focusing on repeating words,
people fail to notice the speaker has changed
C.
Thresholds
1.
What are the absolute and difference thresholds, and do stimuli below the absolute threshold
have any influence?
a.
Shades on our sense are open just a crack
b.
We have restricted awareness of what is going on around us
2.
Absolute thresholds
a.
Absolute thresholds – the minimum stimulation necessary to detect a particular light,
sound, pressure, taste, or odor 50% of the time
b.
Subliminal stimuli – detection less than 50% of the time
c.
Uses
i.
Mosquito ringtones are not likely to be heard by older adults (thresholds
change with age)
ii.
Welsh shopkeepers broadcast annoying sounds to help disperse loitering
teens; these same sounds do not repel older adults
3.
Signal detection
a.
Signal detection theory – predicts when we will detect weak signals
b.
Theorists seek to understand why people respond differently to the same stimuli
i.
Parents hear their newborn’s whimper but fail to hear louder sounds
ii.
Some teachers are more alert to cheating than others
c.
D.
III.
Vision
A.
B.
Situations will affect our ability to detect signals
i.
In war, we will detect movement much more rapidly
ii.
If expecting a text, we will detect the sound much more readily
4.
Subliminal stimulation
a.
Marketing
i.
Speak directly to our brains
ii.
Can influence behavior
b.
Experiment
i.
If flashed with pleasant image or odor, response is positive to “real” image
ii.
If flashed with unpleasant image or odor, response to same “real” image is
negative
c.
Conclusion
i.
Most of our information processing occurs automatically, in the
subconscious mind
ii.
Influence is fleeting
iii.
Subliminal procedures offer littler or no value to advertising
5.
Difference thresholds
a.
Definition – just noticeable difference, the minimum difference a person can detect
between any two stimuli half the time. Detectable difference increases with the size
of the stimulus
b.
Weber’s Law – for difference to be perceptible, two stimuli must differ by a constant
proportion, not a constant amount
c.
Average person’s difference thresholds vary with object
i.
Two lights must differ in intensity by 8%
ii.
Two objects must differ in weight by 2%
iii.
Two tones must differ in frequency by only .3%
Sensory Adaptation
1.
What is the function of sensory adaptation?
a.
Definition – our diminishing sensitivity to an unchanging stimulus
b.
After constant exposure to a stimulus, our nerve cells fire less frequently
2.
Does not occur with eyesight because unbeknownst to us, our eyes constantly flit
a.
A person’s gaze jumps from one spot to another every third of a second
b.
Would we able to secure the eye from moving, the image would somewhat blur and
disappear, reappearing in parts
3.
Purpose
a.
To free ourselves to notice change
b.
Perceive world not exactly as it is, but as it is useful for us to perceive it
c.
Used in TV to grab our attention: cuts, edits, zooms, pans, sudden noises
What is the energy that we see as visible light?
1.
We convert one sort of energy to another
2.
Eyes receive light energy and transduce (transform) it into neural messages
The Stimulus Input: Light Energy
1.
What we see
a.
Not color, but pulses of electromagnetic energy that our visual system perceives as
color
b.
Spectrum of electromagnetic energy: gamma rays, x-rays, ultra-violet rays, “color,”
infrared rays, radar, broadcast bands
2.
Physical characteristics that help determine our sensory experience of them
a.
Wavelength – distance from one wave peak to the next – determines its hue
b.
Intensity – amount of energy in light waves (determined by a wave’s amplitude or
height) – influences brightness
c.
C.
D.
Frequency – the number of complete wavelengths that can pass a point in a given
time, depends on the wavelength (shorter wavelength, higher frequency)
The Eye
1.
How does the eye transform light energy into neural messages?
a.
Process
i.
Light enter the eye through the cornea (protects the eye and bends light to
provide focus)
ii.
Then, through pupil (small adjustable opening surrounded by the iris)
iii.
Then, the iris (colored muscle that adjusts light intake – dilates or
constricts); iris is distinctive and can confirm identity
iv.
Lens (focuses incoming light rays into an image on the retina)
v.
Retina (multi-layered tissue on the eyeball’s sensitive inner surface)
vi.
Lens focuses the rays by changing its curvature in a process called
accommodation
b.
Inverted images
i.
Retina does not “see” a whole image
ii.
Millions of receptor cells convert particles of light energy into neural
impulses and forward those to the brain
iii.
There, the impulses are reassembled into a perceived, upright-seeming
images
2.
The retina
a.
Multi-layered tissue on the eyeball’s sensitive inner surface
b.
Tracking light
i.
Light goes through outer layer of cells (retina)
ii.
Buried receptor cells – rods and cones
iii.
Light triggers chemical changes that spark neural signals
iv.
Activation of neighboring bipolar cells
v.
Bipolar cells activate neighboring ganglion cells
vi.
Axons from ganglion cells converge to form the optic nerve
vii.
Optic nerve carries information to the brain
viii.
Thalamus receives and distributes the information
3.
Blind spot
a.
Where optic nerve leaves the eye there are no receptor cells
b.
Close one eye and you won’t see a black hole
c.
Bain fills in the hole
4.
Rods and cones
a.
Cones
i.
Cluster in and around the fovea (retina’s area of central focus)
ii.
Provide precise pictures
iii.
Perceive color when there is light
b.
Rods
i.
Share bipolar cells, sending combined messages
ii.
Continue working in dim light, hence black and white vision at night
c.
Night vision animals have more rods than cones
Visual Information Processing
1.
How does the brain process visual information?
a.
Process: retina, optic nerve (crosses), thalamus, visual cortex
b.
Misfiring: rubbing right eyelid; brain reads this as light on the left
2.
Feature detection
a.
Neurons in the occipital lobe’s visual cortex receive information from individual
ganglion cells – identifying as edges, lines, angles, and movements
b.
Supercell clusters respond to more complex patterns
c.
Specific areas of the brain respond to faces, shoes, chairs, etc.
3.
E.
IV.
Parallel Processing
a.
Not serial processing – step by step
b.
Parallel processing – at the same time
i.
Visual scene – color, movement, form, and depth – simultaneously
ii.
Facial recognition takes 30% of cortex
iii.
If brain is disrupted with magnetic pulses, face recognition does not occur,
though it can still recognize something simple, like a house
4.
Simplified summary of visual information processing
a.
Scene
b.
Retinal processing – receptor rods and cones  bipolar cells  ganglion cells
c.
Feature detection – brain’s detector cells respond to specific features (edges, lines,
angles)
d.
Parallel processing – brain cell teams process combined information about color,
movement, form, and depth
e.
Recognition – brain interprets the constructed image based on information from
stored images
Color Vision
1.
How does the eye perceive color?
a.
A tomato’s redness is due to the fact that the object rejects red, so it bounces back
b.
Color threshold is low; we can discriminate some 7 million different color variations
2.
Young-Helmholtz trichromatic (three-color) theory
a.
Retina has 3 types of color receptors
b.
Each set is especially sensitive to one of the 3 colors
c.
The 3 colors are red, green, blue
d.
When both red and green sensitive cones are stimulated, we see yellow
3.
Color blindness
a.
Result of lacking red and/or green sensitive cones
b.
Vision is monochromatic or dichromatic instead of trichromatic
c.
Dogs lack receptors for the wavelengths of red, giving them limited dichromatic color
vision
4.
Afterimages
a.
Stare at a green square for a while and then look at a white sheet of paper, you see
red (green’s opposing color)
b.
Hering’s opponent-process theory
i.
Visual information leaves the receptor cells and is analyzed in sets of 3
ii.
Three sets of opponent colors: red-green, yellow-blue, white-black
iii.
Some neurons are turned “on” by red but turned “off” by green and viseversa
5.
Conclusion – color processing occurs in 2 stages
a.
Retina’s red, green, and blue cones respond in varying degrees to different color
stimuli
b.
Signals are then processed by the nervous system’s opponent-process cells, en
route to the visual cortex
Hearing
A.
Overview
1.
Sense of hearing, audition, is highly adaptive
2.
We hear best those sounds with frequencies in a range corresponding to the human voice
3.
Hearing instantly stimulates receptors in the inner ear, comparing to previous experience
B.
The Stimulus Input: Sound Waves
1.
What are the characteristics of air pressure waves that we hear as sound?
a.
Stimulus energy is sound waves – jostling molecules of air, each bumping to the
next
b.
Similar to ripples in a pond
2.
c.
d.
Process
a.
b.
c.
Our ears detect these brief air pressure changes
We hear through air and bone conduction
Ears transform vibrating air into nerve impulses
Strength or amplitude of sound waves determines loudness
Frequency determines pitch
i.
Long waves have low frequency and low pitch
ii.
Short waves have high frequency and high pitch
Measurement in decibels
C.
3.
The Ear
1.
How does the ear transform sound energy into neural messages?
a.
We must convert sound waves into neural activity
b.
Process
i.
Outer ear channels the sound waves through the auditory canal
ii.
To the eardrum (a tight membrane that vibrates with the waves)
iii.
To the middle ear which transmits the eardrum’s vibrations through a piston
made of 3 tiny bones (hammer, anvil, stirrup)
iv.
To the cochlea (snail shaped tube in the inner ear) where vibrations cause
the cochlea’s membrane (the oval window) to vibrate
v.
Vibrations jostle the fluid that fills the tube
vi.
Motion causes ripples in the basilar membrane, bending hair cells lining its
surface
vii.
Hair cell movement triggers impulses in adjacent nerve cells
viii.
Axons converge to form the auditory nerve, which sends neural messages
(via the thalamus) to the temporal lobe’s auditory cortex
c.
Summary: vibrating air, piston, fluid waves, electrical impulses, brain
2.
Hearing damage
a.
Damage to hair cells accounts for most hearing loss
b.
Analogy: shaggy carpet, springs back to action unless exposed to heavy furniture
(loud sound) for a long period of time
c.
Cannot talk over noise – too loud
d.
Sound exceeds 100 decibels, can cause damage
e.
Men more than women suffer hearing damage
f.
Ringing in ears – possible damage
3.
Perceiving loudness
a.
Soft sounds activate a few hair cells attuned to its frequency
b.
Louder sounds activate neighbor hair cells
c.
Brain interprets loudness from the number of activated hair cells
d.
Those suffering from hearing loss still hear loud noises; harder to hear sounds only
should be amplified
4.
Perceiving pitch
a.
What theories help us understand pitch perception?
i.
Place theory – stated by Hermann von Helmholtz, stipulates that different
pitches trigger activity at different places in the cochlea
ii.
Frequency theory – explains the brain reads pitch by monitoring the
frequency of neural impulses traveling up the auditory nerve
b.
Currently accepted explanations
i.
Place theory helps explain how we sense high pitches
ii.
Frequency theory helps explain how we sense low pitches
iii.
Some sort of combination of the 2 for intermediate range pitches
5.
Locating sounds
a.
How do we locate sounds?
i.
Sound will strike one ear faster than it does the other
ii.
V.
If coming from above, below, behind, and equally distant from both ears, we
may make mistakes. That is why we cock our heads. To get a better
sense of location
b.
Deaf individuals have difficulty locating sound
D.
Hearing Loss and Deaf Culture
1.
What are the common causes of hearing loss?
a.
Conduction hearing loss – problems with the mechanical system that conducts
sound waves to the cochlea
b.
Sensorineural hearing loss – damage to the cochlea’s hair cell receptors or their
associated nerves (due to heredity, aging, or prolonged exposure to noise)
2.
Cochlear implants
a.
Only way to restore hearing fro people with nerve deafness
b.
Works by translating sound into electrical signals that, wired into the cochlea’s
nerves, convey some information about sound to the brain
c.
Works best on small children (preschoolers or younger)
d.
Will not work if the brain never learned to hear, in other words, if the person never
heard to begin with
e.
Controversy
i.
Implants help hearing
ii.
Implants take away from the enhancement of other senses. This would
naturally occur upon loss of hearing
iii.
For implants to work, they have to be put in before the child can consent
3.
Living in a silent world
a.
Challenges – people who are deaf and do not have a supportive community, suffer
from low self-esteem
b.
Not the case if part of a supportive community
Other Senses
A.
Touch
1.
Love
a.
Sense of touch is responsible for feeling wanted
b.
Those who are not touched feel depressed and fail to develop normally
2.
Specified locations
a.
A mix of distinct senses
b.
Only pressure has identifiable receptors
c.
Most are variations of the basic four – pressure, warmth, cold, pain
3.
Fooling the brain
a.
If you look at a realistic rubber hand and your own hand, and the rubber hand gets
stroked, you will feel the sensation of being touched
b.
Your brain expects the sensation, therefore, creates it
4.
Kinesthesis
a.
Sense of the position and movement of body parts
b.
Linked to visual stimuli as well as particular nerve endings
5.
Vestibular sense
a.
Monitors head and body position and movement
b.
Located in ear – semicircular canals and vestibular sacs
c.
When spinning motion suddenly stops, these kinesthetic receptors do not
immediately return to normal – dizzy effect
6.
Understanding pain
a.
Biological influences
i.
Purpose – stop behavior, stop the pain
ii.
How it occurs – no one type of stimulus; instead, different nociceptors
iii.
Nociceptors – sensory receptors that detect hurtful temperatures, pressure,
or chemicals
iv.
3.
B.
Taste
1.
2.
C.
D.
Smell
1.
Gate-control theory – spinal cord contains a neurological gate; pain opens
the gate; if you massage the pain, you compete with the pain feeling less
pain
v.
Competing with pain – distracted from pain, feel less; soothed by release of
endorphins, less pain
b.
Psychological influences
i.
Remember peak and end
ii.
Results of study: lengthen the duration of pain, but make it less painful
iii.
Taper end pain instead of shutting abruptly during peak
c.
Social-cultural influences
i.
Seeing pain can trigger pain in ourselves
Controlling pain
a.
Distract the brain – 3D computer generated world, conversation ease focus on pain
b.
Believing “is” reality – placebos work
How do we experience taste?
a.
Various areas of the tongue experience different tastes: sweet, salty, sour, bitter,
umami (savory meat taste)
b.
Linkage to purpose: sweet – energy source; salty – physiological processes; sour –
potentially toxic acid; bitter – potential poisons; umami – proteins
c.
Taste sensors can decrease through alcohol use and smoking
d.
Suggestive information can increase/decrease experience
i.
Wine costs $90 – we think it tastes unusually good
ii.
This doesn’t taste good at all – we are predisposed to not like
Sensory interaction
a.
Smell + taste = flavor
b.
Most senses interact
c.
Synaesthesia – one sort of sensation produces another (hearing sound sees a color)
How do we experience smell?
a.
Process: airborne molecules  receptors at the top of the nose  message to the
brain  temporal lobe’s primary smell cortex and to the parts of the limbic system
b.
Chemical sense
c.
No one distinct receptor for one distinct odor; combo instead
d.
Difficult to describe smell
2.
Experience can determine whether the smell will be considered pleasant or not
3.
Close associations within the brain
a.
Sense of smell close to sense of taste
b.
Sense of smell close to area of brain associated with memory
Perceptual Organization
1.
How did the Gestalt psychologists understand perceptual organization?
a.
Gestalt – German word meaning a “form” or a “whole”
b.
In perception, the whole may exceed the sum of the parts (our brain “connects the
dots”)
2.
Form perception
a.
Figure and ground - we distinguish the figure from its background
b.
Grouping
i.
Proximity
ii.
Similarity
iii.
Continuity
iv.
Connectedness
v.
Closure
3.
Depth perception
a.
4.
5.
How do we see the world in three dimensions?
i.
Mobility comes with depth perception
ii.
Toddlers refused to cross a visual cliff (glass covering drop-off) even to
their mother’s awaiting arms
b.
Binocular cues
i.
Bi = 2; ocular = eyesight; cues = clues
ii.
Judgment of distance
iii.
Retinal disparity – the difference between the message of one eye and the
other; closer to the eyes, the difference is greater; farther apart, less
iv.
3-D exaggerates retinal disparity (one camera shoots for the left; another
for the right); the glasses separate the vision of the eyes
c.
Monocular cues
i.
Horizontal-vertical illusion – given same distance, we tend to think an item
is taller than it is wide
ii.
Higher objects appear farther away
iii.
Relative size – if we assume objects are the same size, then smaller object
is farther away
iv.
Interposition – if one object blocks another, we assume the blocking object
is closer
v.
Linear perspective – parallel lines seem to converge at a distance; the more
they converge, the greater their distance
vi.
Light and shadow – the dimmer of two objects appears farther away
vii.
Relative motion – the farther objects are from the fixation point, the faster
they seem to move
Motion perception
a.
How do we perceive motion?
i.
Brain computes motion partly based on the assumption that shrinking
objects are retreating (not getting smaller) and enlarging objects are getting
closer
ii.
Stroboscopic movement – fast “slides” are reconstructed by our brain as
fluid (animation: 24 still pictures per second)
iii.
Phi phenomenon – Succession of lights creates illusion of movement
b.
Our brain constructs our perceptions
Perceptual constancy
a.
Definition – recognition of objects without being deceived by changes in shape, size,
brightness, or color
b.
Shape and size constancies
i.
Moon illusion/Ponzo illusion – cues to the objects’ distance make the
horizon Moon appear farther away and therefore larger than the Moon high
in the night sky; take away the distance cues, and the object immediately
shrink
ii.
Ames illusion – Adelbert Ames designed a distorted room – the distortion
makes us think that the girls in it are equally distant from our eye when
viewed through a peephole
c.
Color constancy
i.
Color constancy – color remains the same though wavelengths and lighting
shifts
ii.
Color is also relative to other colors
iii.
Animals not brought up in normal color atmosphere have difficulty noting
color shifts and relativity
d.
Lightness constancy
i.
Light is perceived as constant as long as other items receive the same
relative luminance
VI.
VII.
Perceptual Interpretation
A.
Nature v. Nurture
1.
Immanuel Kant maintained that knowledge comes from our inborn ways of organizing
sensory experiences
2.
John Locke argued that through our experiences we also learn to perceive the world
B.
Sensory Deprivation and Restored Vision
1.
We are born with certain sight
2.
Experience develops the rest
3.
Experiment, if only allowed to see diffused light during infancy, restored vision does not truly
restore vision. Something happened during a critical developmental stage that did not allow
for the brain to make the perception connections
C.
Perceptual adaptation
1.
New prescription may make humans dizzy, but after a few days, they adapt
2.
Radical goggles shifting left to right and up to down can still be adapted to (not all animals,
though)
D.
Perceptual Set
1.
How do our expectations, contexts, and emotions influence our perceptions?
a.
Mental predisposition affects perception
b.
Experiments: French fries in a McDonald’s bag taste better; beer told to include
vinegar tastes more bitter
c.
Experience allows us to form schemas (concepts that organize and interpret
unfamiliar information)
i.
We have liked McDonald’s French fries; hence, we think they taste better
ii.
Vinegar tastes bitter; hence, the beer now tastes bitter
2.
Context effects
a.
In sentence structure, we fill in as well
i.
Eel is on the wagon  wheel is on the wagon
ii.
Eel is on the orange  peel is on the orange
b.
Society
i.
Baby is a boy – he is stronger and larger
ii.
Baby is a girl – strong and large may not be adjectives
3.
Emotion and motivation
a.
If feeling tired, a hill will look steeper; a destination, farther
b.
If listening to sad music, perception of a task is more negative
4.
Review
a.
Perception of reality is influenced by social-cultural, biological, and psychological
b.
Social-cultural: cultural assumptions and expectations
c.
Biological: sensory analysis, unlearned visual phenomena, critical period for sensory
development
d.
Psychological: selective attention, learned schemas, Gestalt principles, context
effects, perceptual set
Is There Extrasensory Perception?
A.
Extra-Sensory Perception (ESP)
1.
Definition - perception can occur without sensory input
2.
Includes telepathy, clairvoyance, and precognition
3.
96% of psychologists do not believe exists
B.
Claims of ESP
1.
Paranormal phenomena (psi) include astrological predictions, psychic healing,
communication with the dead, and out-of-body experiences (none of these very “testable”)
2.
Relevant and somewhat testable
a.
Telepathy – mind-to-mind communication
b.
Clairvoyance – perceiving remote events
c.
Precognition – perceiving future events
C.
D.
d.
Psychokinesis (PK) – mind over matter
Premonitions or Pretensions
1.
Chance is really the reason for the “correctness” of predictions
2.
Not accepted as valid by most psychologists
Putting ESP to Experimental Test – and ESP has failed