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Sensation and Perception
Sensation
• The process by which our process by which our sensory systemssensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli receive stimuli from the environment
Sensation• Input comes from the five
senses:
–Visual (Eyes)
–Audio (Ears)
–Cutaneous/Tactile (Touch)
–Olfaction (Smell) (Nose)
–Gustation (Taste) (Tongue)
Receptor Cells
• Each of the five senses is specifically coded to only take in one type of stimulus, whether is be light waves, sound waves, smell, taste, or touch.
Perception
• The process of organizing and interpreting sensory information
• How we recognize, interpret, and organize our sensations
Bottom-Up Processing
•Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation
•This is the sensation part of awareness
Top-Down Processing
•Information processing that focuses on expectations and experiences in interpreting incoming sensory information
•This is the perception part of your awareness
Top Down Processing can lead to errors!
do you see the tiger? (top down) do you see the tiger? (top down) do you see the hidden tiger? (bottom up)do you see the hidden tiger? (bottom up)
do you see the mountains? (top down) do you see the mountains? (top down) do you see the face? (bottom up)do you see the face? (bottom up)
Thresholds
Module 9: Sensation
Absolute ThresholdAbsolute Threshold•A threshold is an edge or a
boundary•For sensations, it is the point
where you either sense a stimulus or don’t
Technically, its “The Technically, its “The minimum stimulus that a minimum stimulus that a person can detect 50% of person can detect 50% of
the time”the time”
Absolute Detection Threshold• The minimum intensity of
energy required to produce sensation in a receptor cell
• Taste: 1 gram of table salt in 500 liters of water
Smell: 1 drop of perfume diffused throughout a three room apartment
• Touch: The wing of a bee falling on your cheek from a height of 1 centimeter
• Hearing: The tick of a watch from 6 meters away
• Vision: A candle flame on a clear night, 30 miles away
•One testable way to determine the thresholds for various people is through SIGNAL SIGNAL DETECTIONDETECTION
• Incremental changes in sound, taste, etc. are made to test for reactions in people. Tone tests Tone tests
(hearing) are an example.(hearing) are an example.
Signal Detection Results• HitHit
– signal present and sensed
• MissMiss– signal present but not
sensed• False AlarmFalse Alarm
– signal absent, but sensed
• Correct RejectionCorrect Rejection– signal absent, and not
sensed
• IE. Frog eye’s have receptor cells that fire only in response to small, dark, moving objects. Theoretically, a frog would starve to death while knee-deep in motionless flies.
Remember…………Remember……………ABSOLUTE …ABSOLUTE
means we either means we either see it, smell it, see it, smell it, taste it….or we taste it….or we
don’t!don’t!
Difference ThresholdDifference Threshold• The minimum difference that a person
can detect between two stimuli 50% of the time
• Also called just noticeable difference
• (JND)(JND)
someone must have turned on another
light!
Hey! Is it just me or did suddenly get a
little brighter in here?!
Ernst Weber and Weber’s Law Weber’s Law • The greater the magnitude of the The greater the magnitude of the
stimulus, the larger the stimulus, the larger the difference must be in order to be difference must be in order to be noticednoticed– IE. If you are carrying 20 lbs. and add
5 lbs., it’s noticeable. If you are carrying 100 pounds and add 5 pounds, it may not be noticeable. You need to add 10 lbs. to 100 pounds to make it noticeable.
Sensory Adaptation• When exposed to a stimuli over
a period of time there will be a diminished sensitivity to it
• If a stimulus is constant and unchanging, eventually a person may fail to respond to it
Example of Sensory Adaptation
• A hot tub – after a certain period of time no longer seems as hot
Let’s see how good your senses are!
TAKE THE AWARENESS TEST ON THE NEXT SLIDE!
Selective Attention• Focusing conscious awareness on a
particular stimulus (sense) to the exclusion of others
Selective Attention Example
• Walking down the hallway – all 5 senses are firing. What grabs your attention?
Selective hearing
• Do you think it exists?
Selective Attention• Focusing conscious awareness on a
particular stimulus to the exclusion of others
• The ability to focus on one stimulus at a time
• Allows a person to function in a world filled with many stimuli
The Visual System: The Nature of Light
Module 9: Sensation
The Visual System: The Structure of the
Visual System
Module 9: Sensation
Cornea• The clear bulge on the front of the
eyeball
• Begins to focus the light by bending it toward a central focal point
• Protects the eye
Parts of the Eye – Cornea
Iris
• A ring of muscle tissue that forms the colored portion of the eye; creates a hole in the center of the iris (pupil)
• Regulates the size of the pupil by changing its size--allowing more or less light to enter the eye
Parts of the Eye - Iris
Pupil
• The adjustable opening in the center of the eye that controls the amount of light entering the eye (surrounded by the iris)
• In bright conditions the iris expands, making the pupil smaller.
• In dark conditions the iris contracts, making the pupil larger.
Parts of the Eye - Pupil
Lens• A transparent structure behind the pupil;
focuses the image on the back of the eye (retina)
• Muscles that change the thickness of the lens change how the light is bent thereby focusing the image
• Glasses or contacts correct problems in the lens’ ability to focus.
Parts of the Eye - Lens
Nearsighted - Myopia
Farsighted - Hyperopia
Retina• Light-sensitive surface with cells that
convert light energy to nerve impulses
• At the back of the eyeball
Parts of the Eye - Retina
Receptor Cells
• These cells are present in every sensory system to change (transduce) some other form of energy into neural impulses.
• In sight they change light into neural impulses the brain can understand.
• Visual system has two types of receptor cells – rods and cones
• Visual receptor cells located in the retina
• Can only detect black and white
• Respond to less light than do cones
Rods
• Visual receptor cells located in the retina
• Can detect sharp images and color
• Need more light than the rods
• Many cones are clustered in the fovea.
Cones
Fovea
• The central focal point of the retina
• The spot where vision is best (most detailed)
Parts of the Eye - Fovea
Visual Processing in the Retina
Visual Processing in the Retina
Visual Processing in the Retina
Visual Processing in the Retina
Optic Nerve
• The nerve that carries visual information from the eye to the occipital lobes of the brain
Parts of the Eye – Optic Nerve
Blind Spot
• The point at which the optic nerve travels through the retina to exit the eye
• There are no rods and cones at this point, so there is a small blind spot in vision.
Parts of the Eye – Blind Spot
Retinal Implant
The Visual System: Color Vision
Module 9: Sensation
Color Vision
• There are two theories of color vision:
–Trichromatic Theory
–Opponent-Process Theory
Can you see what is in the middle?
Trichromatic TheoryYoung-Helmholtz Theory
• Cones are pre-set to be sensitive to RED, GREEN, and BLUE. All of the colors that we see are combinations of those three colors.
Color Deficient Vision• People who lack one of the three
types of cones• Usually the red or green receptors
are missing• Usually referred to as color blindness
• In inherited and found more in males
Red-Green Color Blindness
Opponent-Process Theory
• Sensory receptors in the retina come in pairs:–Red/Green–Yellow/Blue–Black/WhiteWhite
• Only one side is “on” at a timeOnly one side is “on” at a time
Opponent Process Theory
ON” “OFF”red greengreen red blue yellow yellow blue black whitewhitewhite white black
Afterimage Effect
Opponent-Process Theory
• If one sensor is stimulated, the other is inhibited
• If one sensor is over-stimulated, and fatigues, the paired sensor will be activated, causing an afterimage
Hearing: The Nature of Sound
Module 9: Sensation
Sound
•Sound, like light, comes in waves
•Sound is vibration•Features of sound include:
–Pitch–Hertz–decibels
Pitch
• A sound’s highness or lowness in tone
• Dependent on the frequency of the sound wave – the more “waves per second” the higher the frequency or pitch
• Is measured as hertz (Hz)
Hertz (Hz)
• A measure of the number of sound wave peaks per second; measures “frequency”
• Determines the pitch of the sound
• Human hearing goes from 20 Hz to 20,000 Hz
Low Pitch
• Wave peaks are far apart
Human hearing goes from 20 Hz to 20,000 Hz although some ears (and speakers) are
better than others
High Pitch
• As pitch increases, so do the number of waves
Remember - Human hearing goes from 20 Hz to 20,000 Hz note: a kilohertz is 1,000 hertz
so 20 kilohertz equals 20,000 hertz
Decibel (dB)
• A measure of the height of the sound wave
• Determines the loudness of the sound
• Sometimes called amplitude
Hearing: The Structure of the
Auditory System
Module 9: Sensation
PINNA
• It collects sound and directs it into the outer ear canal.
Also called the auricle. The
visible part of the outer ear.
Parts of the Ear – Auditory Canal
• The opening through which sound waves travel as they move into the ear for processing
• Ends at the eardrum
Auditory Canal
THE MIDDLE EAR
Eardrum
•Also called the tympanic membrane. A thin membrane that vibrates when sound waves reach it.
• it transfers sound vibration from the air to the tiny bones of the middle ear
•Can be damaged by objects in the ear or exceptionally loud noises
Parts of the Ear – Tympanic Membrane
Ossicles
•Three tiny bones that transfer sound waves from the eardrum to the cochlea
•Hammer, anvil and stirrup–Fun fact: the stirrup is the smallest bone in the human body – only .25 cm
Parts of the Ear - Ossicles
Oval Window
•The point on the surface of the cochlea which receives the sound vibration from the ossicles
•As the oval window vibrates, the fluid in the cochlea vibrates.
Parts of the Ear – Oval Window
• The Ossicles amplify the vibration of the eardrum
Cochlea
•A hearing organ where sound waves are changed into neural impulses (transduction)
•The major organ of hearing•Filled with fluid; a snail
shaped body tube
Parts of the Ear - Cochlea
Hair Cells• The receptor cells for hearing in the
cochlea that change sound vibrations into neural impulses
• Transduction!
Movement of the fluid causes the hair cells to move which causes TRANSDUCTION!
Parts of the Ear - Hair Cells
Auditory Nerve
• The nerve that carries sound information from the ears to the temporal lobes of the brain
Parts of the Ear – Auditory Nerve
Semicircular Canals
•Organs in the inner ear used in sensing body orientation and balance (vestibular sense)
•Relies on fluid in the canals•Spinning in circles disrupts
the fluid.
Parts of the Ear – Semicircular Canals
Divisions of the Ear
• Ear’s structure can be divided into:
–The outer ear
–The middle ear
–The inner ear
Divisions of the Ear
Divisions of the Ear
Divisions of the Ear
Parts of the Ear•Sound waves to Outer Ear-
•Ear Canal, Eardrum (waves bounce on membrane)
•Middle Ear- hammer, anvil, stirrup
•Small bones vibrated by waves
•Oval Window (membrane vibrates)
• Inner Ear- sound waves ripples fluid in cochlea and activates hair cells
Problems with hearing• Conduction deafness (middle ear damage)
• Nerve deafness (hair cell or auditory nerve damage)
How do we hear?Place Theory-Place Theory- different frequencies in sound waves cause vibrations atdifferent placesplaces in the cochlea
High Frequencies
Low Frequencies
Frequency Theory-Frequency Theory- different frequency of the sound wave
vibrates the inner ear at a different rate
EUSTACHIAN TUBE
• A tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear.
Hearing: Sound Localization
Module 9: Sensation
Localization of Sound
• Locating where sound is originating from
• Done through two cues:
–Which ear hears the sound first?
–Which ear hears the louder sound?
Localization of Sound
Problems with hearing• Conduction deafness (middle ear damage)
• Nerve deafness (hair cell or auditory nerve damage)
• Cochlear Implant
Other Senses: Taste
(Gustation)
Module 9: Sensation
Taste• Taste is a chemical sense.
• The little bumps on our tongues are actually called papillae
• Inside some of these papillae are clumps of taste cells.
• These clumps of cells are actually the taste buds.
Taste• On average, adults have about 7,500 taste buds.
• These receptor cells are located in the tongue and in the mouth.
• When food dissolves on these receptors, TRANSDUCTION occurs
• Damaged taste receptor cells are replaced within a few days to 2 weeks
• Taste Sensations
–sweet
–sour
–salty
–bitter
- umami (savory-msg)
Supertasters
• People with an abundance of taste receptors
• Approximately 25% of the population
Nontasters
• People with a minimum of taste receptors
• Taste with less intensity than the rest of the population
• Approximately 25% of the population
Other Senses: Module 9: Sensation
Smell• Smell is a chemical sense.• Olfactory receptors/cells in the
upper nasal passages detect molecules in the air.
• Taste and smell interact to produce flavor.
Olfactory Cells
• The chemical receptor cells for smell
• Located in the nasal passages
Smell
Smell
Smell
Other Senses: Touch
Touch• Touch receptors are on the skin• Four basic skin senses are
– Pain– warmth– cold– pressure
• All skin sensations are a combination of these four basic senses
Sensitivity of Diff body to pain
Most Sensitive
• Back of knees
• Neck region
• Bend of elbow
Least Sensitive
• Tip of the Nose
• Sole of foot
• Ball of thumb
• Pain messages travel on one set of nerve fibers containing pain gates.
• The gates are open when pain is felt.
• Other sensory messages go through another set of fibers.
• The non-pain fibers can close the pain gates to stop the sense of pain.
Suppressing Pain (this is a link…in case its not working….)(this is a link…in case its not working….)
Gate-control Theory of Pain
• Pain messages travel on one set of nerve fibers containing pain gates.
• The gates are open when pain is felt.
• Other sensory messages go through another set of fibers.
• The non-pain fibers can close the pain gates to stop the sense of pain.
Other Senses: Body Senses
Module 9: Sensation
Kinesthetic Sense•The system for sensing
the position and movement of individual body parts
•Relies on receptor cells from the muscles and joints
•One’s leg “falling asleep” is a disruption of the kinesthetic sense
Vestibular Sense• The system for sensing body
orientation and balance• Relies on fluid in the semicircular
canals of the inner ear• Spinning in circles disrupts the
fluid.
Parts of the Ear – Semicircular Canals
The End