Download Chapter 5 Sensation and Reality

1. Chapter 5 Sensation and Reality
Properties of Sensory Systems
Eyes (vision)= light sensory system
Senses
Sensitivity to senses
Vision
Perception of color
Hearing mechanism
Chemical senses
What do the senses have in common?
Data Reduction System (DRS)
Sensory images or other senses us DRS
DRS=
1. Selects
2. Analyzes
3. Filters information until only important details remain.
Transducers= device that changes one kind of energy to another
Sense are receptive to Range of Energy
We only perceive some forms of energy (example- specific types of wave)
Sensory AnalysisAs senses process info…
The senses divide the world into important Perceptual Features
Which are Basic stimulus patterns
Example: Vision – Features include- Lines shapes, edges, spots and colors
DRS
1. Select
2. Analyze
3. Filter
When a pattern is broken the senses recognize the features
Perceptual Features- Pop Out when a pattern is present
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Analysis (part of Data Reduction)
Sensory Analysis
1st Senses use – Feature detectors- detect patterns
Code it – After sense info is analyzed
It is converted into Neural Messages understood by the brain (AKA Transduction)
Phosephenes = visual sensations- caused by mechanical stimulation of retina)
Eye’s receptor cells are sensitive to pressure as well as light
Sensory Localization = (means) types of sensations you experience depends on which brain
area is activated- (Vision , Auditory, taste, touch)
Sense Organs Eyes, Ears- info creates Sensations
Perception takes place in Brain (patters = Perceptions)
Psycho-PhysicsMeasures of physical stimuli
Q: What’s the minimum amount of energy necessary for sensation to occur?
A: Absolute Threshold
Absolute Threshold
Thresholds define limits of sensory world
*Sensation = immediate response in the brain
Dog whistles = upwards of 40,000 hertz (Beyond Human awareness)
Humans senses from 20 Hertz = Vibrations per second
To 20,000 Hertz
Difference Thresholds
Q: How much must a stimulus change before it is noticeably different?
JND= Just Noticeable Difference
The smallest difference between stimuli that we can detect is called JND.
Weber’s Law- The amount of change needed to produce JND is a constant proportion
of the original stimulus.
“That's to say that, if the intensity of a sensation (of sight, or smell, or sound, or taste,
or touch) is doubled from an initial value and the sensation noted, the intensity will
have to be doubled once more to give the same impression of increase in sensation.”
Sensitivity to hearing /Pitch/Loudness is greater than taste
Perceptual Defense & Subliminal Perception

Thresholds vary for different people & could change
Perceptual DefenseThe resistance to perceiving threatening or disturbing stimuli
The McGinnies study- (1994) Dirty words take longer to be recognized.
Seems that we resist info that causes Anxiety, discomfort, or embarrassment.
Limen
(Threshold or Limit) for awareness
Below the normal Threshold = Subliminal
Subliminal Perception
Demonstrated by insertion of images, Emotional Images caused altered impressions
Too fast to be recognized
Below the level of conscious awareness


Subliminal Persuasion- Selling Popcorn and Coke at movies… (Author says it doesn’t
work)
Rock Music and Subliminal Messages
Back Masking- perceived unconsciously (Vokey and Read 1985 said no effect)
Subliminal Perception does occur
“Subliminal effects are usually small and short-lived, and they mainly affect simple
judgments and general measures of overall arousal.”
Messages that people can perceive consciously have far stronger persuasive effects.
Vision: Catching Some RaysWavelengths of light = Visible Spectrum
“Electro magnetic energies to which the eyes respond”
Visible Light Starts @400 nano meters
=One billionth of a meter
=Purple or violet
Longer Light waves = Blue, Green, yellow, orange, and red =700 nanometers
Hue= Basic color categories – red orange yellow, green, blue, indigo, violet
Corresponds to light’s wavelengths
Saturation= pure color = narrow band of light
Brightness= amplitude, height of light waves
Taller more energy, more color, brighter more intense
Structure of the Eye:
Eye is like a Camera
Lens to focus images on a light sensitive layer at back of a closed space
Back layer is= a layer of photo receptors in retina- (light sensitive cells)
Focus is done at front of eye via the Cornea
Cornea = clear membrane, bends light inward
Lens – makes small adjustments – Shape is altered by muscles for focus
Muscles use Accommodation- change Camera’s change distance from film
http://www.eye-floaters.com/theeye-nearandfarvision.php
problem is the shape of cornea and how it is projected onto the back of the eyeball or retina
Astigmatic
Near Sighted
Myopic= Longer (than usual) eye
Concave lens-spreads light rays just enough to increase eyes focal length
FarsightedThe convex lens increases refraction (bending)
Returns point of focus to Retina.
Astigmatic:
(lens) or Cornea not symmetrical) eye parts of vision are sharp
And parts are unfocused
Lens is Unsymmetrical
Visual Problems
Presbyopia
Old vision
Lens becomes less flexible
Farsightedness to aging
Focusing is affected by the shape of the eye
Hyperopia – (Farsightedness= eye is too short)
Can’t focus nearby objects- trouble reading up close
Distant objects will be sharp
Myopia- (nearsightedness) eyeball is too long
Images fall short of the retina
Can’t focus on distant objects
Close objects are in focus
Astigmatism- Cornea lens is misshapen
Part of vision is focus
Part is also fuzzy
Eye has more than one focal point
All are corrected by lenses that change the path of light
LASIK- Lasor Assisted Insitu keratomileusis
Reshapes and stretches the cornea
Increases degree of cornea bending light
Light ControlThe Iris- controls amount of light entering
Colored – Muscle that expands and contracts
Changes size of pupil
Allows more light
Dilates= enlarged pupil- allows more light
Constrict= narrow less light enters the pupil
Anatomy of the Eye
Retina
Vitreous Humor- Jelly like substance Fills the eyeball
Photoreceptor cells
Rods
Cones
Fibers of Optic Nerve
Ganglion Cell
Amacrine Cell
Bipolar Neuron
Horizontal Cell
Anatomy of Eye
Optic Nerve
Retinal Arteries
Retinal Veins
Retina
Lens
Blind Spot
Fovea
Ciliary Muscle
Aqueous Humor
Iris
Cornea
Vitreous Humor
Sclera
Page 183
“How the Brain Sees the World”
David Hubel and Torstem Wiesel
Say- Vision Acts more like a computer than T.V.
Recorded cell activity
In Brain’s visual cortex (cats & monkey subjects)
Noted area of retina where cells responded
Collected data on light & firing of nerve impulses
Found cells in the brain act as Feature Detectors
Process- the brain analyzes info into lines, angles, shading, movement…
Then- other brain areas combine Features into meaningful visual experiences.
Rods and Cones:
Light does not fall on rods and cones it must pass layers of retina/
 Receptor cells
Rods
Cones
100 million each eye
6.5 million in each eye
No Color
Work best in bright light
Black and White = Pure Rod Vision
Color Sensations
More Sensitive to light than cones
Fine Detail
Allows sight in dim light
Mostly at center of eye
Sensitive to movement
Fovea contains only cones
Good for Peripheral Vision
Most sensitive to yellow, green color
Contain light sensitive visual pigments
(Theory Tri-color) 3 types of cones- Fire nerve
impulse@ different rates to produce color

Break down when struck by light
sensations

After image of Flash bulbs= “Bleading”

Night Vision- Rod Pigment= increase
Rhodopsin- Vitamin A enhances Retinal
sensitivity (see link)
Each eye has a Blind spot
Where optic nerve leaves the eye <no receptors>
Visual Acuity = Sharpness
Normal 20/20
20’ distance you can see what average people see at 20 ft.
20/40 = you can only see at 20 feet what most people see at 40 feet
20/200 = correct= legal blindness
FoveaCup shape on retina
Only has cones
Concentration of cones = greatest visual acuity
Pixel
Dot of light
More pixels = sharper image
Peripheral Vision:
“Rod Vision” – not very sharp
Area outside the Fovea gets light
Side visionRods most numerous ca (around) 20° from center of retina
Tunnel Vision = Loss of peripheral vision
Color Vision
Yellow-green spectrum
Cones most sensitive
Rods not sensitive to color but colored light- blue green is most sensitive
At night blue can be seen best
Color Theories=
Tri-chromatic Theory = what happens in the eye
3 types of cones
Each sensitive to red green blue
Other colors are combos
Problem
There are 4 colors of light- Red, Green, Blue, Yellow
You can get these by mixing
Doesent Address all aspects of colored light
Opponent Process Theory:
Vision analyzes color as either or messages
Red or green
Yellow or Blue
System can produce either
Black or white
Explains what happens –
Optic pathways + Brain
After info leaves Brain
How colors are analyzed – after eye ball
After Images
Visual sensations that persist after stimulus is removed
“Seeing spots”
Relates to Opponent Process TheoryFatigue caused by one response causes after image of opposite color system
Bothe theories apply
Tri-color
3 visuals Pigments= light sensitive chemicals
Red, Green, or Blue
3 types of cones- Fire nerve impulse@ different rates to produce color sensations
Mechanical View of Color Sensation
Colors are influenced in the brain by other colors nearby
= Simultaneous color contrast
Affect perception of color (p 186)
Color Blindness
Can not perceive colors
Lacks cones or cones don’t function
Rare
Color Weakness= people can’t see certain colors
8% of males = red – green weakness (see red and green as yellow – brown)
1% of women
Genetic
Affecting Red and Green + Blue
Pigments in Cones
Ishihara- Test – I.D.s Color Blindness
Contrasts- colors through simple patterns circles/squares
Light and Dark Adaptation (Rods)
The dramatic increase in retinal sensitivity
Eyes adjust- 30-35 minutes for maximum sensitivity
Complete darkness = 100,000 times more sensitive
Contain light sensitive visual pigments
Night Vision- Rod Pigment= increase Rhodopsin- Vitamin A enhances Retinal
sensitivity
Break down when struck by light
After image of Flash bulbs= “Bleading”
Red light- helps people adapt to dark- it doesn’t stimulate rods
It doesn’t stimulate the rods
 As the retinal component of rhodopsin is derived from vitamin A, a deficiency of
vitamin A causes a deficit in the pigment needed by rod cells. Consequently, fewer
rod cells are able to sufficiently respond in darker conditions, and as the cone cells
are poorly adapted for sight in the dark, blindness can result. This is nightblindness.
Hearing: “Good Vibrations”
Hearing- Collects info
Stimulus for hearing = waves in air
Peaks – Compression
Valley’s = Rarefaction
Sound waves = vibrating objects
Rhythmic = movement of air molecules
Sound does not travel in a Vacuum
Frequency of Sound Waves = # of waves per second
Corresponds to pitch (the tone of a sound)
Amplitude= height of a sound wave
Tells how much energy it contains
Relates to loudness (sound intensity)
Sound waves converted to Nerve Impulse
Pinna (visible, external part of ear)
Acts as a funnel to concentrate sound
Tympanic Membrane (eardrum)
Sound waves collide
Auditory Ossicles (3 small bones) link eardrum to cochlea= Snail shape organ Vibrate
1. Malleus- hammer
Links eardrum with Cochlea
2. Incus- Anvil
3. Stapes- Stirrup-- Oval windowTo cochlea- is organ of hearing- inside tiny hair cells = Sterocilia
detects waves in fluid
To cochlea- is organ of hearing- inside tiny hair cells = Sterocilia detects waves in fluid
Part of Corti- (center of cochlea)
Steriocilia:
Hair cells brush against the Tectorial Membrane when waves ripple through the
fluid surrounding the organ of Corti.
Then to the Auditory nerve fibers-
Frequency Theory- of Hearing
As pitch rises Nerve impulses of same Frequency are fed to auditory Nerve
Example – 800 hertz (= number of vibrations per second)- tone = 800 nerve impulses
Place TheoryHigher & lower tones excite specific areas of the Cochlea
High tones at the base of Cochlea
Low tones move hair cells near outer tip of Cochlea
Hair Cells respond to area of greatest movement
Deafness- 2 types of deafness
Conduction Deafness
= Transfer vibration to inner ear is weak
Eardrum or Ossicles are damaged
Hearing Aid- makes sounds clearer + louder
Stimulation (deafness)
Loud sounds (Damage Hairs)
85 Decibels- may cause permanent loss
Temp-Threshold Shift
120 decibels Partial transitory hearing
loss
Nerve deafness= damage to hair-cells or
auditory nerve
Tinnitus- ringing- buzzing sensation
Sense of Smell and Taste:
Olfaction (Smell)
Gustation (Taste)
Chemical Senses  receptors that respond to chemical molecules
Olfactory Receptors:
Receptors- Airborne molecules
300-400 smell receptors
Thread like fibers inside nose
5 million nerve fibers
Upper nasal passages
Receptor Proteins- are sensitive to molecular stimulation
Combination of Odor receptorsCan detect 10,000 different odors in humans
“Lock and Key Theory” Shape of receptors impact smells
Also Location of receptors
Number of activated receptors tells how strong an odor is.
Anosmia- Anosmic (no sense of smell)
Defective smell
For single odor
Suggest these are specific receptors for specific odors
Molecularly- some odors have similar shape
Sent likes and dislikes are learned
Pheromones- “A Sixth Sense”
Animals – affected
 Mating
 Sexual Behavior
 Recognition of Family members
 Territorial marking
Vomeronasal Organ- (VNO)
 The sense organ for pheromones
 Receptors in septum
 Produces vague feelings
Well being
Attraction
Unease
Anxiety
Affect General Mood
May cause women’s menstrual cycles to become synchronized
Taste:
4 basic Taste Sensations
Sweet Least Sensitive
SaltSourBitter- Most sensitive
Flavor
Taste buds= taste receptors cells
Top of tongue and around the edges
Chewing- taste buds nerve impulses to brain
Lock and Key matching
Sour = Saltiness  triggered by direct flow of atoms
Taste-Sensitivity = how many taste buds on tongue
Age association
Cells live only days then are replaced
Taste preferences are acquired
Somoesthetic Senses- Body Feel
1. Touch Skin senses
Pain
Balance
2. Kinesthetic Senses (movement)
Receptors in muscles
Receptors in Joints
Detect body position + Movement
3. Vestibular Senses
Receptors in the inner Ear for balance, gravity, Acceleration
Skin 5 Sensations
Light + touch
Pressure
Pain
Cold
Warmth
Receptors- shape specialize
Skin has 200,000 nerve endings for temperature
500,000 touch + pressure receptors
3 million for pain
# of skin receptors = skin receptivity
Increased Density of receptors in:
Lips
Tongue
Hands
Genitals
Pain- (Warning System- says the body is being damaged)
Lots of Pain Receptors
Varied Distribution
232 Pain points per 5 square centimeters (behind knee)
184 in Buttocks
60 in the thumb
44 on nose
Pain fibers are also on internal organs
Visceral Pain is felt on the surface of the body = Referred Pain
Somatic Pain (Bodily)
2 types
1. Large nerve fibers
Skin, Muscles, Joints, Tendons
Sharp bright and fast
From specific body areas
Warning System- says the body is being damaged
2. Small Nerve Fibers
Slower, nagging, aching, widespread, very unpleasant
Repeat is more painful
Reminder System
Reminds brain that the body has been injured
Phantoms Live Here
Missing limb continues to feel as if it is present
Brain still senses limb
Brain can reorganize the senses
Dynamic TouchArcs
Sensation from skin + Kinesthetic info from muscles + Tendons
We can use objects like extension of our bodies
Vestibular System
Inner Ear
Motion Sickness
Semi-circular canals
Sense organs-for balance
Semi Circular Canals Sense organs for balance, filled with fluid
Ampullae- contains crista and fiber