Chapter 5 Sensation and Reality - Point Loma High School



Chapter 5 Sensation and Reality

Properties of Sensory Systems

Eyes (vision)= light sensory system

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 Analysis-

As 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

Perceptual Features- Pop Out when a pattern is present

When a pattern is broken the senses recognize the features

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-Physics-

Measures 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 Defense-

The 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 Rays-

Wavelengths 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



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

Farsighted-

The 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

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 Control-

The 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

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 |

|Break down when struck by light |rates to produce color 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

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

Fovea-

Cup 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 vision-

Rods 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 Theory-

Fatigue 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 night-blindness.

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 window-

To cochlea- is organ of hearing- inside tiny hair cells = Sterocilia detects waves in fluid

[pic]

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-

[pic]

[pic]

[pic]

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 Theory-

Higher & 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 |Stimulation (deafness) |

|= Transfer vibration to inner ear is weak |Loud sounds (Damage Hairs) |

|Eardrum or Ossicles are damaged |85 Decibels- may cause permanent loss |

| |Temp-Threshold Shift |

|Hearing Aid- makes sounds clearer + louder |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 receptors-

Can 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

Salt-

Sour-

Bitter- 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

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 Touch-

Arcs

Sensation from skin + Kinesthetic info from muscles + Tendons

We can use objects like extension of our bodies

[pic]

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

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Senses

Sensitivity to senses

Vision

Perception of color

Hearing mechanism

Chemical senses

DRS

1. Select

2. Analyze

3. Filter

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Presbyopia

Old vision

Lens becomes less flexible

Farsightedness to aging

Anatomy of Eye

Optic Nerve

Retinal Arteries

Retinal Veins

Retina

Lens

Blind Spot

Fovea

Ciliary Muscle

Aqueous Humor

Iris

Cornea

Vitreous Humor

Sclera

Receptors- shape specialize

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